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Recent research on Nikopolis

Geophysical prospection as a landscape archaeological approach to an ancient city in Epirus (Greece) and the role of geophysical prospection for the research of Roman urbanism

by Dr. Michael Teichmann (Author) Konstantinos L. Zachos (Author)

Textbook 2017 146 Pages

Archaeology

Excerpt

Table of Contents

List of Figures and Tables

Abstract

Introduction
Aims and Objectives
Structure

Chapter 1
Geographical setting
Geology
Geomorphology
Climate
Topography of the city

Chapter 2
Research on Nikopolis

Chapter 3
Field procedure
Scientific principles
Magnetometry
Earth resistance survey
Grids
Sampling interval and instruments: Magnetometry
Discussion of the equipment
Sampling interval and instrument: Earth resistance survey
Factors limiting the geophysical survey

Chapter 4
Data processing and software

Chapter 5
Survey areas and results
Area 1
Area 2
Area 3
Area 4
Area 5
Area 6
Comparison with the data of the Dutch survey
Area 7
Area 8
Area 9

Chapter 6
The role of geophysical prospection for the research of Roman urbanism
Case studies

Chapter 7
Conclusion - Outlook on further research on Nikopolis

Appendix 1
The battle of Actium and the foundation of Nikopolis
The state of Epirus at the time of Nikopolis’ foundation

Appendix 2
Important ancient sources on Nikopolis

Appendix 3
Dekker, van de Locht (2008), 82. Quotation

Appendix 4
Acknowledgements

Reference List

Ancient sources

Oral sources

Online resources

List of Figures and Tables

Fig. 1: Location of Nikopolis in Epirus - satellite image, source: Google Earth

Fig. 2: The battle of Actium, 2nd September 31 BC, tactical movements, source: Chrysostomou, Kefallonitou (2005), 7.

Fig. 3: Topographic map of Nikopolis, Zachos, 2015, 2.

Table 1: Nikpolis survey areas - overview

Fig. 4: Survey areas in the local context

Fig. 5: Location of Nikopolis in the regional context

Fig. 6: Geological model of the Nikopolis region after King et al. (1993), source: cited in Dekker, van de Locht; 2008, 10.

Fig. 7: Contemporary climate chart for Preveza, source: weatheronline.co.uk.

Fig. 8: Plan of the city´s urban fabric, source: Zachos, 2015, 100.

Fig. 9: Augustan city wall (after restoration), southern side

Fig. 10: Odeion of Nikopoli, source: Zachos, 2015, 117.

Fig. 11: Theatre of Nikopolis, situated in the “northern suburb”, source: Zachos, 2015, 75.

Fig. 12: Remains of the Nikopolis aqueduct close to the village of Archangelos, source: Zachos, 2015, 104.

Fig. 13: North Nymphaion, source: Zachos, 2015, 108.

Fig. 14: “Domus of Manius Antoninus”, source: Zachos, 2015, 133.

Fig. 15: Ground plan of the House of of Manius Antoninus; source: Zachos, 2015, 132.

Fig. 16: Southern early Byzantine city wall, outer side

Fig. 17: Ground plan of Basilica B, source: Zachos, 2015, 185.

Fig. 18: Ground plan of the House of ekdikos Georgios, source: Zachos, 2015, 137.

Fig. 19: Drawing of the Nikopolis Isthmus seen from the north by Carl Haller von Hallerstein (1810) Bib. Nationale et Universitaire Strassbourg, source: Isager (2001a)

Fig. 20: Site plan of Nikopolis, published by Philadelphus, source: cited in White (1991), 300.

Fig. 21: Leica 500 GPS measuring of the grid corners

Fig. 22: English Heritage caesium-magnetometer cart, source: Linford et al. (2007), 152.

Fig. 23: Vienna Institute for Archaeological Science caesium-magnetometer cart, source: 40 http://www.univie.ac.at/Idea/geophysik.html

Fig. 24: University of Kiel fluxgate magnetometer cart

Fig. 25: Nikopolis survey area 7 site - survey on difficult ground

Fig. 26: Spatial context of survey area 1, south of the early Byzantine walls The figure shows the processed data

Fig. 27: Magnetometer survey in the north-western grids of the area 1 (in the background the metal fence close to the road)

Fig. 28: Fragment of a monolithic column shaft made of white marble, close to the greenhouse of area

Fig. 29: Spolia in the lower layers of the western early Byzantine wall

Fig. 30: Area 1 magnetic raw data

Fig. 31: Area 1 processed magnetic data (clipped and interpolated)

Fig. 32: Interpretation of area 1 magnetic data in the spatial context

Fig. 33: Area 1 interpretation of the geophysical data projected on the hypothetical city grid

Fig. 34: Spatial context of survey area 2 south of the early Byzantine walls

Fig. 35: Area 2 magnetic raw data

Fig. 36: Area 2 processed magnetic data (clipped and interpolated)

Fig. 37: Area 2 interpretation of the magnetic data combined with the projected city grid

Fig. 38: Area 2 interpretation of the magnetic data - detail of the building complex

Fig. 39: Survey area 3, processed magnetic data in the spatial context

Fig. 40: Area 3 magnetic raw data

Fig. 41: Area 3 processed magnetic data (clipped and interpolated)

Fig. 42: Area 3 interpretation projected on the hypothetical city grid

Fig. 43: Area 4 processed data in spatial context

Fig. 44: Area 4 western grid raw data

Fig. 45: Area 4 western grid processed data (clipped and interpolated)

Fig. 46: Area 4 eastern grid raw data

Fig. 47: Area 4 eastern grid processed data (clipped and filtered)

Fig. 48: Area 4 interpretation of the processed data

Fig. 49: Area 5 A and 5 B in spatial context

Fig. 50: Area 5 A seen from the south

Fig. 51: Area 5 B seen from the north-west

Fig. 52: Area 5 A magnetic raw data

Fig. 53: Area 5 A processed magnetic data (clipped and interpolated)

Fig. 54: Area 5 A interpreted

Fig. 55: Area 5 A interpreted and projected on the hypothetical city grid

Fig. 56: Area 5 B magnetic raw data

Fig. 57: Area 5 B magnetic data (clipped and interpolated)

Fig. 58: Area 5 resistance raw data

Fig. 59: Area 5 processed resistance data (slightly clipped and interpolated)

Fig. 60: Area 5 B interpretation of the processed magnetic data

Fig. 61: Area 5 B interpretation of the processed resistance data

Fig. 62: Area 6 processed magnetic data in spatial context - standing remains of the thermal building visible in the southeast

Fig. 63: Northern thermal complex, eastern wing, situated immediately to the west of area

Fig. 64: Northern thermal complex in a drawing by Thomas Leverton Donaldson (originally published 74 by Leake, depicting the site in the early 19th century) - plan, source: Chrysostomou, Kefallonitou (2005), 51.

Fig. 65: Survey area 6 seen from the north-west

Fig. 66: Wall remains hidden in the bramble bushes of the survey area

Fig. 67: Geophysical survey results presented by Dekker, van de Locht (2008)

Fig. 68: Features identified by the Dutch survey

Fig. 69: Area 6 magnetic raw data

Fig. 70: Area 6 processed magnetic data (clipped and interpolated)

Fig. 71: Area 6 resistance raw data

Fig. 72: Area 6 processed resistance data (clipped and interpolated)

Fig. 73: Area 6 interpretation of the magnetic data

Fig. 74: Area 6 interpretation of the resistance data

Fig. 75: Area 6 alternative visualisation of the processed resistance data showing the building complex

Fig. 76: Possible reconstruction of Roman landscape after the foundation of Nikopolis (artist’s impression by Sander Weernink), source: Dekker, van de Locht (2008), 109.

Fig. 77: Possible reconstruction of (early) Byzantine landscape on the Nikopolis Isthmus (artist’s impression by Sander Weernik), source: Dekker, van de Locht (2008), 110.

Fig. 78: Area 6 interpretation of the December 2008 survey in comparison with the Dutch survey results

Fig. 79: Survey of area 6 in heavy rain

Fig. 80: Area 7 A and 7 B processed data in spatial context

Fig. 81: Area 7 A seen from the north

Fig. 82: Area 7 B seen from the west

Fig. 83: Recent excavations in the stadion showing the attachment of a semi-circular end in a second building phase

Fig. 84: Recent excavations in the stadion showing remains attributable to the earlier building phase

Fig. 85: Surface find from area 7 A. Fragment of Samian Ware with potter´s stamp `LA SEST´

Fig. 86: Area 7 A magnetic raw data

Fig. 87: Area 7 A processed raw data (clipped and interpolated)

Fig. 88: Area 7 B magnetic raw data

Fig. 89: Area 7 B processed magnetic data (clipped and interpolated)

Fig. 90: Area 7 A and 7 B interpretation

Fig. 91: Axial relationship of city gate and victory monument, the interpreted road in area 7 A (in yellow) prospected on this line is the continuation of the road named as feature 7 B (in blue)

Fig. 92: Stadium radial substructure walls at the western end of the stadion

Fig. 93: Area 7 interpretation of the magnetic data combined with the plan of the stadion, substruction walls are visible in the west

Fig. 94: Area 8 processed data in their spatial context

Fig. 95: Area 8 seen from the north-west

Fig. 96: Area 8 resistance survey under difficult conditions

Fig. 97: Area 8 resistance raw data

Fig. 98: Area 8 processed resistance data (clipped and interpolated)

Fig. 99: Area 9 processed data in their spatial context

Fig. 100: Area 9.1 magnetic raw data

Fig. 101: Area 9.1 processed magnetic data (clipped and interpolated)

Fig. 102: Area 9.2 magnetic raw data

Fig. 103: Area 9.2 processed magnetic data (clipped and interpolated)

Fig. 104: Area 9.3 magnetic raw data

Fig. 105: Area 9.3 processed magnetic data (clipped and interpolated)

Fig. 106: Area 9.4 magnetic raw data

Fig. 107: Area 9.4 processed magnetic data (clipped and interpolated)

Fig. 108: Map of the major archaeological sites mentioned in chapter 7, source: Google Earth

Fig. 109: Map of the major archaeological sites mentioned in chapter 7 - detail: sites in Italy, source: Google Earth

Table 2: Main sites discussed in chapter 7 and methods applied

Fig. 110: Interpretation plan of the geophysical prospection undertaken at Falerii Novi, source: http://www.southampton.ac.uk/archaeology/img/Falerii_Plan.jpg

Fig. 111: Visualisation of geophysical prospection data from Forum Novum, source: Gaffney et al. (2004), Pl

Fig. 112: Visualisation of magnetometer data from Butrint, source: Bescoby et al. (2004), 191.

Fig. 113: Interpretation of magnetometer data from Butrint, source: Bescoby et al. (2004), Pl. 1.

Fig. 114: Visualisation of magnetometer data from Wroxeter, source: Gaffney et al. (2000), 84.

Fig. 115: Georeferenced greyscale image of the resistivity mapping in the civil town of Carnuntum; visualisation of GPR data from Carnuntum, source: Neubauer, Eder-Hinterleitner (1997), 184.

Fig. 116: Visualisation of GPR data from Flavia Solva, source: Groh et al. (2002), 86.

Fig. 117: Interpretation of GPR data from Flavia Solva, source: Groh et al. (2002), 88.

Fig. 118: Visualisation of maritime magnetometer data from the Baia, source: Paoletti et al. (2005), Pl. 3.

Fig. 119: Area 6 combined interpretation of resistance and magnetic data

Fig. 120: Area 5 B combined interpretation of resistance and magnetic data

Fig. 121: Aerial photography of Nikopolis from the west (photo Schoder), source: White (1991), 300.

Fig. 122: The Augustan victory monument - reconstruction, source: Zachos (2003), 69.

Fig. 123: Preveza Peninsula with traces of Roman centuriation after Stein (2001), cited by Zachos, source: Zachos (2007b), 160.

Fig. 124: Map showing the location of the roman towns Nikopolis, Butrint and Patras, source: Google Earth

Fig. 125: Drawing of the Tabula Peutingeriana showing Nikopolis labeled Acta Nicopoli; surrounding road network, source: Bowden (2003), 18 (after Ugolini 1937)

Fig. 126: Provenience of participants in the synoicism, source: Chrysostomou, Kefallonitou (2005), 12.

Fig. 127: Agora of Kassope.

Fig. 128: View from Kassope to the south. Ambracian Gulf to the left, Preveza Peninsula in the centre, Ionian Sea to the right.

If no source is stated, photos were taken and figures designed by the authors. Photos may not be reproduced without the permission of the authors.

Abstract

Between the 11th and the 21st December 2008 a geophysical survey was carried out on the site of the ancient city of Nikopolis (Epirus - Greece), founded in the late first century BC, and in its surrounding landscape. The archaeological potential of nine areas of interest was evaluated and the nature of present archaeology characterized. During the project, an area of approximately 49200 square meters was surveyed. The results of fluxgate magnetometer and earth resistance survey are presented within this book. Main results are the discovery of several archaeological features (probably roads and walls) within the walled city area, the discovery of adjacent buildings belonging to a bath complex situated north of the ancient city and the discovery of a road connecting the city with the stadium and the sacred grove in the northern suburb. The results are presented in the context of the research on Nikopolis. The role of geophysical prospection for the research on Roman urbanism is discussed as the general framework of the presented case study.

This text is based on the MA dissertation of Michael Teichmann undertaken as part of the requirements for the degree of MA in Landscape Archaeology, GIS and Virtual , submitted at the University of Birmingham in 2009. The primary scope of this publication is to make the results of the geophysical prospection project available to the wider public.

The general structure of the thesis was maintained and only minor editorial amendments have been undertaken. The discussion of the role of geophysical prospection for the research on Roman urbanism reflects the state of research in 2009 and does not take into account more recent developments. Konstantinos L. Zachos, who directed the research and works of conservation and restoration of the monuments of Nikopolis for numerous years, co-authors this publication. Therefore, the part on Nikopolis was slightly updated to take into account recent research results.

Introduction

The archaeological site of Nikopolis is situated in Epirus, a region in the northwest of modern Greece (Fig. 1).

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Fig. 1: Location of Nikopolis in Epirus - satellite image, source: Google Earth.

Nikopolis was founded to commemorate the victory of Gaius Julius Caesar Octavianus, the later Emperor Augustus, over Cleopatra VII and Marcus Antonius on the 2nd of September 31 BC in the decisive sea battle of the Roman civil wars fought off the shores of the Actian peninsula (Zachos, 2015a, 12-18) (Fig. 2).

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Fig. 2: The battle of Actium, 2nd September 31 BC, tactical movements, source: Chrysostomou, Kefallonitou (2005), 7.

The city (Fig. 3) was the first foundation of the first princeps and therefore played an important ideological role (Purcell, 1987, 71; Bowden, 2007; Zachos, 2015a, 22-27), which resulted in a metropolitan character and the adornment with numerous prestige buildings.

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Fig. 3: Topographic map of Nikopolis, Zachos, 2015, 2.

The city flourished in the early imperial age and was turned into the provincial capital of Epirus, probably in the early second century AD. Barbarian raids affected the city from the third century AD onwards, but a refortification of the city´s core led to a new heyday in early Byzantine times in the late fifth and early sixth century AD. Few inhabitants remained in the former city until the tenth or eleventh century AD.

Today Nikopolis is one of the most important archaeological sites of Greece dating to the Roman and Byzantine period. The former urban area of the Augustan town is estimated to cover approximately 130 ha with a suburban area of the same size which was partly built up (Hoepfner, 1987, 129).

Nikopolis is regarded as a key site that could reveal important insights not only into the regional history of Epirus, but also for a better understanding of Augustan culture and town planning and the process of acculturation often described as Romanization (Hoepfner, 1987, 133; Bowden, 2007, 135). The appreciation of the site´s outstanding universal value is documented by the enrolment in the Tentative List of UNESCO´s world cultural heritage in 2003 (http://whc.unesco.org/en/tentativelists/270/). Financial support was granted by the European Union for the preservation of the site at least since 1991 (Douzougli, 2007).

Aims and objectives

In 2008, the Nikopolis Scientific Committee, following the excavations and surface survey investigations that took place on the site for about fifteen years, along with restoration work on monuments and the conservation of portable finds and mosaic floors, considered that the conditions for a proposal of an integrated management program “Master Plan” for the site and its conversion into an archaeological park were matured. The character of the “Master Plan” is essentially a land use plan, in the sense that it focuses on the organization of the site as a whole, through the formation of monumental nuclei and their interconnection, the placement of reception and visitors’ infrastructure, the organization of a network of pedestrian paths, fencing some areas off, water supply, electricity and the configuration of specific traffic settings in the modern road network. A basic principle underlying the study's reasoning was that the roads of the ancient city shall be used approximately for the modern visitors’ pedestrian paths, since the recent archaeological research had identified the gates of the walls and the main arteries of the city's urban fabric. A second principle governing the study was to create nuclei with monuments that would be visited, since most of the archaeological site remains unexposed by archaeological excavations. A basic principle was also the combination of the access to the site and its monuments by the visitors, alongside farmers' access to their fields, since a large part of the site, with the exception of the area within the early Byzantine fortification, belongs to the farmers of the neighboring villages[1]. Since the study for the proposal carried out by the Nicopolis Scientific Committee had to take into account all the archaeological data and because it was not possible to carry out excavations in the short term at the points, where modern interventions were foreseen, such as the construction of buildings and parking lots, it was considered appropriate to seek the assistance of modern technology and sciences. For those reasons, the Committee has asked the Laboratory of Geophysical Satellite Studies and Archaeo-Environment of the Institute for Mediterranean Studies (IMS) / Foundation of Research & Technology (F.O.R.T.H.) of which Dr. Sarris is the director, to undertake geophysical prospection in areas designated by the staff of the Technical Office of the Committee, which was ordered to provide the necessary assistance and all archaeological information to the team of geophysical research.

Between the 11th and the 21st December 2008 geophysical survey was carried out on nine selected areas within the walled area and in vicinity of the ancient city to evaluate the archaeological potential of these possible sites and characterize archaeological features present as far as possible (Table 1; Fig. 4). The surveys focused on the following areas:

1. This area is located near the southern wall of the Early Christian fortification, southeast of the so-called "Beautiful Gate". According to the proposal, the plan was to build here a parking lot, for the convenience of the visitors, who will reach the site from the city of Preveza.
2. This area is located inside the Early Christian fortification at the southwest corner. The [1] Regarding the Master Plan which was prepared by the Technical Office of the Scientific Committee of Nikopolis and was approved, according to the Archaeological Law, by the Central Archaeological Council, see Zachos, K.L., Tsakoumis, Chr., Kappa, Ch., Kyrkou, Th., Krokidas, P., and Papavasileiou , K., in print, , Αρχαιολογικό Πάρκο Νικόπολης: Πρόταση αναβάθμισης του ιστορικού τοπίου στο πλαίσιο ενός ευαίσθητου οικοσυστήματος, in: Πρακτικά ημερίδας «Αρχαιολογικά Πάρκα: Εμπειρίες και Προοπτικές»; Zachos, K. in print, Το Αρχαιολογικό Πάρκο Νικόπολης: Η διαχείριση και ανάδειξη ενός εκτεταμένου ερειπιώνα της Αυτοκρατορικής και Πρωτοβυζαντινής εποχής στην Ελλάδα, in: What’s New in Roman Greece, Proceedings of the International Conference held in Athens Ion October 8-10 , 2015. object of the research at this point was to detect the continuation towards east of the decumanus maximus which was located by excavations inside the South Gate of the fortification, the so called "beautiful gate", as well as to investigate the possibility of the existence of a cardo along the west wall of the fortification. According to the proposal, a path for the visitors was planned to be constructed along that direction.
3. This area is located along the western wall of the Early Christian fortification and north of the main West Gate. The research aimed to investigate the existence of a cardo and other remains along and near the wall.
4. This location is situated southwest of the so-called Bishop's Palace. This edifice, first mentioned by W. Leake, has been addressed with different names in different times. Recent excavations have shown that it is a Roman house occupying an entire insula of the urban fabric. The first building phase of the house dates back to the beginning of the 1st century. AD. After the most recent investigations the edifice was named domus of Ekdikos Georgios after an inscription on a mosaic floor. The aim of the research at the southern part of the complex was to investigate the possibility of the existence of a road due to a pavement that was detected by earlier excavations.
5. This area is located northeast of the house of Manius Antoninus, a luxurious residence, which occupies approximately an entire insula. To the east of the house, a cardo was found, which along its axis had a drainage system (cloaca) and pavement. In the northeast of the road excavations revealed the remains of a building, parts of were covered by the road in a later building phase. The aim of the investigation in this area was to locate and to characterize the nature and the extension of the architectural remains.
6. This area was planned to be organized as the main entrance for visitors to the archaeological park, providing all the appropriate facilities such as parking lot, guardians’ house, ticket booths and lavatories. This location was chosen for two reasons, first because it is close to the Preveza-Igoumenitsa highway leading to the Egnatia road and secondly because it was deemed appropriate for the visitor to enter the ancient city from the ceremonial road that started from the North Gate, crossed the North Cemetery and ended up in the suburb, where all the infrastructure was located for the organization of the Actian games.
7. The subject of the research in this area near the stadium was of a dual nature. First, to investigate the possibility of tracking the continuation of the road from the North Cemetery to the stadium, and secondly to investigate elements within the stadium associated with the recent excavations carried out there, which revealed at least two building phases of the monument.
8. At this location near the main entrance of the Victory Monument a parking lot was planned, according to the proposal. It was therefore necessary to investigate the site beforehand concerning the existence of ancient remnants.
9. The area is located on a hill near the shores of the Ambracian gulf, named after the owner of a fortified house (κούλια = fortified house), which stood on top of the hill during the period of the Ottoman occupation. The hill is cultivated with olive trees, having a spectacular view of the ruins of Nikopolis. According to the proposal, the Committee intended to erect an Institute for the Research of Roman and Early Christian Antiquities in Greece on a property, which was to be donated by the Municipality of Preveza to the Ministry of Culture.

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Fig. 4: Survey areas in the local context.

Magnetometer survey was used as the principal investigation method. In addition, earth resistance survey and Ground Penetrating Radar (GPR) were applied on limited scale to gain additional information. The results of the magnetometer and resistance survey are presented in this thesis in their historical, archaeological and methodological context.

Structure

Chapter 1 gives an overview on the geographical setting and natural preconditions of Nikopolis.

The known archaeological remains of the city are described briefly to raise the awareness of the archaeological frame of the survey and to facilitate the contextualization of the survey results. References to recent publications on the major monuments are provided as it is not the scope of this book to discuss all known monuments in detail. In Chapter 2 the history of the research of Nikopolis is outlined. Chapter 3 describes the field procedure of the geophysical survey. Chapter 4 is dedicated to data processing and software. In Chapter 5 results and interpretation of the data are presented.

In Chapter 6 the case study of Nikopolis is embedded in a wider methodological discussion. The question to which extent geophysical prospection can be successfully applied to improve our knowledge on towns from classical antiquity is discussed.

In Chapter 7 general conclusions are drawn, and an outlook on possible further work on the site of Nikopolis as well as on the prospects of geophysical survey on Roman urban sites is presented.

Appendix 1 contains additional information on the foundation of the city and its history through the course of time. It may be read before proceeding to Chapter 2.

Appendix 2 provides a selection of historical primary sources on Nikopolis in English translation.

Appendix 3 contains a longer quotation of a survey report by Dekker, van de Locht (2008) regarding area 6 (Chapter 5).

In Appendix 4 acknowledgements are stated.

Chapter 1

Geographical setting

Nikopolis is situated on the northern edge of the so-called Preveza Peninsula, which separates the Ionian Sea (to the west) from the Ambracian Gulf (to the east) (Fig. 5).

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Fig. 5: Location of Nikopolis in the regional context.

Geology

The Ambracian Gulf is a graben, separated from the Ionian Sea by numerous uplifts. One of these is the Preveza Peninsula. Immediately to the north of the city a valley forms the “Nikopolis Isthmus”, on which the northern suburb of ancient Nikopolis was constructed. Proceeding further north from the valley, a further uplift area is encountered, regarding a model proposed by King (Fig. 6) (King et al., 1993 cited in Dekker, van de Locht, 2008). Following King, the Preveza Peninsula is being uplifted while the Ambracian Gulf is subsiding (King et al., 1993 cited in Dekker, van de Locht, 2008). Recent research questioned this model (Pashos, 2003 cited in Dekker, van de Locht, 2008) interpreting the southern edge of the Nikopolis Isthmus as a fault, and not as domes, as proposed by King. Latest research suggests that these models are not `mutually exclusive´ and proposed that `north of the Nikopolis Isthmus a domed structure is located that is cut off by a fault or fault zone´ (Dekker, van de Locht, 2008, 45). Oldest deposits in the vicinity of Nikopolis are Triassic evaporates and Jurassic limestone (Dekker, van de Locht, 2008, 13), while the Preveza Peninsula is dominated by `interbedded mudstone, sandstone, marlstone and pebbly conglomerate´ (Janssen et al., 2005, 5).

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Fig. 6: Geological model of the Nikopolis region after King et al. (1993), source: cited in Dekker, van de Locht (2008), 10.

Geomorphology

The Nikopolis Isthmus is a valley of asymmetrical shape, slightly inclined towards the Ambracian Gulf. The isthmus is delimited in the north by steep slopes. The northern slope is more pronounced and steeper than the southern slope. Two valleys discharge sediment on the plain from the north forming alluvial fans (Dekker, van de Locht, 2008, 38). The southern slope is much shorter and ascends to a plateau on which the ancient city of Nikopolis is situated.

Climate

Due to the high mountains, which dominate the landscape of Epirus, the local climate is mainly Alpine with continental influences close to the sea (Fig. 7). The local microclimate of Nikopolis is described as `mild Alpine with warm, wet summers and temperate winters´ (Kootker, 2007a, 8) or as `a very dry one with seasonal heavy rainfall´ (Dekker, van de Locht, 2008, 50).

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Fig. 7: Contemporary climate chart for Preveza - source: weatheronline.co.uk.

Topography of the city

Lacking any predecessor town, whose structures would have to be respected, Nikopolis seems to have been planned from scratch (Bowden, 2007). The city was composed of four centuries, each measuring twenty per twenty actus (one actus equals 120 Roman feet or 35.5 m) allowing the construction of twelve cardines (north-south roads) and four decumani (eastwest roads) (Fig.8).

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Fig. 8: Plan of the city´s urban fabric, source: Zachos, 2015, 100.

The width of an excavated cardo is 7.40 m (25 Roman feet). The principal roads (decumanus and cardo maximus) had a doubled width. The principle orientation of the city was nineteen degrees east of north (Zachos, 2007). As the ancient city gates are known and roads were unearthed in excavations, the main axes and orientation of the street grid can be reconstructed with some reliability. This is meant by the “projected street grid” which is referred to in Chapter 5.

City walls were delimiting the city in the north, east and south (Fig. 9).

Fig. 9: Augustan city wall (after restoration), southern side.

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The walls are slightly irregular, which seems strange for a planned city. Another curiosity is that the western city wall may not have been executed for centuries (Zachos, 2007; Zachos, 2015a, 87-89). An aqueduct is seen as the western limit of the town and it seems that the openings between the arcades have been closed in a hurry in times of military threat in late antiquity (Zachos, 2015a, 87). Therefore, it is obvious that the city walls were not meant to serve any practical military purpose in their original layout, but were meant to be symbols of a free city. This phenomenon fits well with the Augustan ideology of a new era of peace. Another example of a city wall with representative gates that did not serve practical purposes, dating to Augustan times, can be found at Ariminum (today Rimini). The odeion (covered music hall) (Fig. 10) is dated at the first half of the 2nd century (Zachos et. al., 2015a, 69).

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Fig. 10: Odeion of Nikopolis; source: Zachos 2015, 117.

An initial phase of the theater (Fig.11) (Krinzinger, 1987; Kontogianni, 2007; Zachos, 2015a, 75-80; Zachos et al. 2015b), a gymnasium (Zachos, 2015a, 74) and the stadion (Zachos, 2015b) situated in the “northern suburb” are to be dated in Augustan times.

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Fig. 11: Theatre of Nikopolis, situated in the “northern suburb”; source: Zachos, 2015, 75.

The victory monument (Zachos, 2003; Zachos, 2007, 39; Zachos, 2015a, 63-68) can be dated more exactly by a dedicatory inscription and was probably erected between the 11th of January 29 BC and the 16th of January 27 BC (Schäfer, 1993, 247). The aqueduct, which transported water over 45 km from the springs of the Loyros River near the modern village of Ayios Georgios to Nikopolis, was constructed in the 1st century AD, probably under the reign of Nero (Zachos, 2015a, 101-105). A second building phase is Hadrianic (Zachos, 2015a, 105) (Fig. 12).

Fig. 12: Remains of the Nikopolis aqueduct close to the village of Archangelos; source: Zachos, 2015, 104.

Further significant remains date to the second century AD: The North Bath (Zachos, 2015a, 84-85) (see Chapter 5: area 6) and two monumental fountain complexes (nymphaia) on either side of the decumanus maximus inside the Western Gate were erected (Zachos, 2015a, 107-112) (Fig. 13).

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Fig. 13: North Nymphaion; source: Zachos, 2015, 108.

The so called “Domus of Manius Antoninus” may date to the same period. (Zachos, 2015a, 129-135) (Fig. 14 - 15; see in addition Chapter 5).

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Fig. 14: “Domus of Manius Antoninus”, source: Zachos, 2015, 133.

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Fig. 15: Ground plan of the House of Manius Antoninus, source: Zachos, 2015, 132.

Major restoration work was undertaken in the theatre. The Central Bath inside the city was erected at the end of the 2nd or at the beginning of the 3rd century AD (Zachos, 2015a, 124- 128). Due to the military threats, the arcades of the aqueduct delimiting the city in the east seem to have been closed to fortify the city, maybe in the second half of the third century AD (Zachos, 2015a, 87).

The Augustan walls, including the fortified aqueduct have a length of approximately 5 km and would have required numerous soldiers and inhabitants to be defended effectively (Trombley, 2007). Therefore, the construction of the inner, early Byzantine city walls was initiated, reducing the fortified city area to approximately a fourth of the former size (Zachos, 2015a, 167-173; Chalkia, 2013). While the northern and eastern walls were restored Augustan walls, the southern and western walls were new constructions (Fig. 16). The length of the early Byzantine walls, including the reused Augustan elements is 2072 m (Zachos, 2015a, 167; Chalkia, 2013).

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Fig. 16: Southern early Byzantine city wall, outer side.

This major building project was certainly an imperial project of regional importance, while the inhabitants might have had to shoulder the financial burdens (Bowden, 2003). Three building phases of the walls can be stated and construction started probably in the 2nd half of the fifth century AD, the third building phase seems to have been interrupted by the Vandal attack and was continued afterwards (Hellenkemper, 1987; Gregory, 1987; Kefallonitou, 2007, 304; Chalkia, 2013). The erection of the new walls will have changed the perception of the city by its inhabitants drastically (Bowden, 2003).

The phase of wall construction was followed by a period in which numerous basilicas (Basilica B as example in Fig. 17) were erected within the inner Byzantine city (Chalkia, 2013; Zachos, 2015, 174-194; Papadopulou, 2015). The basilicas, adorned with elaborated mosaics, testify the rising power of the Christian church

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Fig. 17: Ground plan of Basilica B, source: Zachos, 2015, 185.

One basilica, linked with a graveyard, was situated outside the late antique walls to the south (Chalkia, 2015) . Besides the erection of churches some of the private houses (domus) were enlarged and adapted to the preferred styles of late antiquity (Pavlidis, 2015) (Fig.18).

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Fig. 18: Ground plan of the House of ekdikos Georgios, source: Zachos, 2015, 137.

The construction of churches and noble peristyle houses came to end in the mid sixth century (Gilkes et al., 2007, 226-227; Chalkia, 2013). Afterwards only very few buildings state the presence of humans at the site, as very simple houses in the south-east of the inner city, dating to the seventh to ninth century AD, show.

Chapter 2

Research on Nikopolis

The oldest report on a visit to the ruins of Nikopolis goes back to Cyriacus of Ancona. He visited the site in 1436, but did not report in detail on what he encountered (Irmscher, 1987, 370; Zachos 2015a, 42).

The first known excavations were undertaken by the French in 1798 in a form that we may describe as “treasure hunting”. French Republican troops were present at Nikopolis in the course of a military campaign against Ali Pasha’s Ottoman- Albanian troops (Curlin, 2010). A decisive battle was fought on the 23rd of October 1798 at Nikopolis between the ancient North wall and the hill of Michalitsi and later on at Preveza. Finds were selected for the French emperor and the building activity of Ali Pasha.

More detailed reports go back to the early 19th century (compare Isager, 2007): E. Dodwell, a member of the Society of Dilettanti, visited Nikopolis in 1801 briefly and reports to have seen the remains of the theatre, a circus and an aqueduct. He further explains that in his days spoliation of the site was undertaken on behalf of Ali Pasha. F. Pouqueville states in his travel reports published in 1820/1821 to have seen the remains of standing houses, the well- preserved city walls, a stadion, a circus for gladiator games and naumachiae (naval combats) as well as temples and further upstanding buildings (Dodwell and Pouqueville summarized in Irmscher, 1987).

Pouqueville´s description is of particular interest as the location of the circus is unknown today, as are the temples, which could have been standing remains of other buildings misinterpreted by Pouqueville as his descriptions are to be treated with great caution due to his scarce reliability. Carl Haller von Hallerstein visited Nikopolis in 1810. A drawing (Fig. 19) shows the Nikopolis Isthmus seen from the north with the theatre in the foreground.

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Fig. 19: Drawing of the Nikopolis Isthmus seen from the north by Carl Haller von Hallerstein (1810). Bib. Nationale et Universitaire Strassbourg, source: Isager (2001a).

Until the 20th of October 1912 Epirus was part of the Ottoman Empire and only then conquered by the Greek army. Excavations at Nikopolis started already in 1913 under the direction of A. Philadelphus (Chrysostomou, Kefallonitou, 2005). His excavations soon revealed the so called “basilica A” as well as the late antique complex called “Bishop’s palace” (Bowden, 2003, 29). The monument of Augustus was partly excavated and interpreted as a Corinthian temple (Zachos, 2001; Zachos, 2003).

A first overview plan (scale 1: 5000) of the site goes back to these first years of research and was drawn by two engineers in 1921 and published by Philadelphus in 1926 (Fig. 20) (quoted in White, 1991).

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Fig. 20: Site plan of Nikopolis, published by Philadelphus, source: cited in White (1991), 300.

Throughout the 1920s and 1930s the excavations were continued and focused mainly on the early Christian monuments, which were the archaeologists´ main research priorities (Bowden, 2003). During the Second World War, Epirus was occupied by Italian troops. Ten plans and detailed sketches were designed by military engineers (White, 1987; White, 1991). Small scale research was undertaken until the late 1970s with a focus on early Byzantine churches. The site was partly under cultivation and to a good extent inaccessible due to dense vegetation until the early 1980s. The situation started to improve with the first International Conference on Nikopolis held at Preveza in 1984 (Chrysos, 1987). One result was the foundation of a Scientific Committee of Nikopolis, which undertook the task to coordinate further research (see above).

Already in the early 1980s the role of non-destructive prospection techniques for the future exploration was underlined (Wiseman, 1987). A large-scale field survey, supported by geomorphological research (Jing, Rapp, 2003), satellite image interpretation (Wiseman, 1987; Vining, Wiseman, 2006) and geophysical prospection (Wiseman 2001, 52) was initiated in 1991 by J. Wiseman (Boston University) and K. Zachos (12th Ephorate of Prehistoric and Classical Antiquities), exploring the hinterland of Nikopolis (Moore, 2001; Stein, 2001; Wiseman, 2001; Wiseman, Zachos, 2003).

From 1988-1993 topographical mapping of the paleochristian remains was undertaken, followed by excavations at the southern side of the early Byzantine city walls (Smyris, Kefallonitou, 2007), the so-called Basilica B of bishop Alkisson (Papadopoulou, 2007) and at the city walls by the 8th Ephorate of Byzantine Antiquities (Kefallonitou, 2007). The 12th Ephorate of Prehistoric and Classical Antiquities has carried out systematic small-scale excavations of the Roman monuments with further results presented at a second international colloquium in 2002 (Zachos, 2007; Douzougli, 2007; Kyrkou, 2007). As one of the tasks for the new millennium, the Greek government has announced the development of the major archaeological sites. Therefore, a management plan for the site of Nikopolis is under development with the aim to create an archaeological park (see above). With this background, the Institute of Geo- and Bioarchaeology (IGBA) of the VU University Amsterdam (www.falw.vu.nl/igba) undertook several projects dealing with restoration issues (Kootker, Kars, 2005; Kootker, 2007a; Kootker, 2007b) and the development of site management plans. A further focus of the IGBA was the reconstruction of the former vegetation and geomorphologic processes on the Nikopolis Isthmus from 2004 onwards, including geophysical survey close to the northern thermal complex (Janssen et al., 2005; Dekker, van de Locht, 2008). The geophysical prospection presented here has to be regarded in context with these recent developments.

Chapter 3

Field procedure

The team consisted of seven persons, so that two groups could measure in parallel most of the time. Heavy rainfall was predominant during the fieldwork, interrupted by some dry and sunny intervals. The soil was water-saturated and puddles formed during the peaks of rainfall.

Scientific principles

As the scientific principles and field procedure of geophysical survey are extensively treated in numerous introductions to this field of research (for example Clark, 1996; Neubauer, 2001; Schmidt, 2002; Gaffney, Gater, 2004; Sarris, 2008), an overview is given as brief as possible.

Magnetometry

Magnetometer survey is a so called “passive” shallow-depth geophysical prospection method, as existing physical properties of the Earth´s magnetic field are measured. It is based on the potential field theory.

The Earth possesses a geomagnetic field whose axis is defined by the magnetic poles, consisting of three components: the main magnetic field, a smaller external field and a local field. The local magnetic field, which is most relevant for archaeological prospection, is constant in contrast to the other fields.

All materials have a magnetic susceptibility, caused by their physical properties, showing to which extent the material is magnetized in an active magnetic field due to inductive and remnant magnetization. Fluxgate gradiometers - as used for this project - measure the vertical component of the magnetic field, while alkali-vapor magnetometers measure the total absolute magnitude of the local field (David et al., 2008, 21). Buried archaeological features may possess magnetic properties contrasting with their surroundings. Magnetized iron oxides can be found for example in soils caused by bacteria (Fassbinder, 1994) and thermoremanent magnetization remains after heating over the Curie Point (565 degree Celsius for magnetite) resulting in a strong magnetization (Neubauer, 2001). This is of particular importance for the detection of fired clay, as brick walls or cooking places. Highly sensitive instruments are used to measure the contrast of the magnetic fields, which can be spatially mapped during the data processing. The unit of the magnetic flux density of the geomagnetic field is the SI unit nanotesla (nT) with picotesla (pT) as subunit (Sarris, 2008). The method works on a relative scale.

Earth resistance survey

Earth resistance survey is a so called “active” shallow-depth geophysical prospection method, as an electric current is induced and the conductivity and resistivity between probes measured. The penetration depth depends on the probe spacing. A pair of twin probes with a probe spacing of 0.5 meters has been proven as a convenient standard (David et al., 2008, 25) and was used for this project, while a pair of fixed electrodes is placed in a distance of at least 30 times the distance between the mobile probe pare (in this case 15m) to the closest measuring point. It was developed in 1970 by Aspinall and Lynam. This configuration leads to a shallow penetration depth of approximately 1m. Numerous other probe constellations (such as wenner, dipole-dipole, square, pole-dipole and schlumberger) exist, but are rarely used for archaeological prospection. The choice of the appropriate array depends on the nature and depth of the archaeological targets, subsoil properties, depth of the investigation and size of the survey area (Sarris, 2008, 1914).

The method is based on the variation of electrical conductivity, which is an inherent physical property of all materials. Factors that influence the conductivity are moisture and a specific, material-immanent ability to conduct a current. Archaeological features like walls and roads are high resistance anomalies as their compactness and material constraints the conduction of the current, while ditches whose fill is generally more humid, metal pipes and drains possess a higher conductivity and are therefore low resistance anomalies (Gaffney, Gater, 2004). `Soil resistance anomalies are defined as the variations or disturbances of the electric field or the current density, which are caused by the existence of the subsurface targets of different geoelectric characteristics. ´ (Sarris, 2008, 1914).

Grids

Grids for the measurements were set out by triangulation following the Pythagorean Theorem. “Standard grids” of 20 x 20 meters (David et al., 2008, 19) were used when appropriate, but grid size could be adapted to local requirements. Pegs marking the outer corner points of the grids were measured with a Leica 500 GPS (Fig. 21). The spatial accuracy of the post-processed GPS data is in a range of approximately 20 centimeters.

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Fig. 21: Leica 500 GPS measuring of the grid corners.

Sampling interval and instruments: Magnetometry

The sampling interval for magnetometer survey was 0.5 meters with a line-spacing of 0.5 meters. Points were measured in the same direction as single traverse in the single shot mode (each measurement was taken by the surveyor). The chosen sampling interval can be seen as a kind of standard interval which was often chosen in those years as a compromise of data resolution and survey time required (compare for example: Piro et al., 2003; Gordan, 2009). A smaller sampling interval was recommended by English Heritage and is a standard by now (David et al., 2008, 8).

Surveying in zig-zag mode would have speeded up the survey and real-time data capturing could have increased the sampling density, but as both of these options tend to increase the staggering of data (compare: Hounslow, Chroston, 2002; David et al., 2008, 23), it was decided to opt for the better data quality.

A FM256 Fluxgate Gradiometer (http://www.geoscan-research.co.uk/page34.html) and a Bartington Grad601-1 Single Axis Gradiometer (Bartington, Chapman, 2004; http://www.bartington.com/products/Grad601singleaxisgradiometer.cfm) were used as devices for the magnetic survey. Both instruments have a sensor with two fluxgate magnetometers, the vertical magnetometer separation of the FM256 is 0.5 meters, while the Grad601 has a separation of 1 meter, allowing the detection of features buried deeper in the ground. The penetration depth of the FM256 is approximately 1.0 - 1.5 meters while the penetration depth of the Grad601 is up to approximately 3 meters under best conditions (for the calculated response compare Bartington, Chapman, 2004, 21 f.).

Discussion of the equipment

Regarding the used instruments, two issues will be addressed briefly:

1. Advantages and disadvantages of single hand-held instruments in comparison with multi-sensor units.
2. Advantages and disadvantages of fluxgate magnetometers in comparison with alkali-vapor magnetometers.

Numerous institutions undertaking research-focused geophysical prospection tend to use cart-based multi-sensor units, sometimes equipped with a Differential GPS as English Heritage (Fig. 22), the University of Vienna (Fig. 23) and the University of Kiel (Fig. 24) (Linford et al., 2007; Neubauer, 2001; Erkul et al., 2004; David et al., 2008).

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Fig. 22: English Heritage caesium-magnetometer cart, source: Linford et al. (2007), 152.

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Title: Recent research on Nikopolis