In the course of the extensive survey of Sikyonia (1996-2002), more than 250 archaeological sites were recorded and mapped, including settlements, forts and watch/signal towers, roads, sanctuaries, quarries, aqueducts and cisterns, terracing walls, and other types of remains.
The political boundaries of ancient Sikyon, based on written testimonia, archaeological remains and the natural topography, are defined by the Corinthian Gulf to the north, the Nemea River to the east, the Sythas River to the west, and the peak of Evangelistria (ancient Thyamia), the mount Gavrias and the Isomata of Kephalari to the south, thus encompassing an approximate area of ca. 360 km². This area includes two mountain ranges, Trikaranon (modern Evangelistria) and Vesiza, which are separated by the river valley of Nemea, and two plains, one to the west of Vesiza and to the east of Kyllene, and a second one along the coast, proverbial for its fertility. Over 80% of the land of Sikyon is mountainous and semi-mountainous, with a gradual ascent (in “marine terraces”) from sea level to the altitude of 1100 m in the southwest and 700 m in the southeast.
Roads suitable for wheeled traffic connected Sikyon to its neighboring cities as well as to more distant districts, following for the most part natural passes and the physical relief with the “straight road” to Phlious, mentioned by Pausanias along the course of the Asopos River, being the most characteristic example. A second road, of southwestern direction, followed the course of the Nemea River, while two more followed the ridge of the Trikaranon range. The number of roads leading to the interior of the Peloponnese is impressive, and can be partly explained by the strategic location of Sikyonia for the military campaigns of the Lacedemonians and their allies to the north of the Isthmus. The construction of these roads involved substantial infrastructure works, as in the case of the road which led from the Sikyonian Plateau to Phlious via Titane, where the natural narrow ridge was consolidated by successive, strong retaining walls in order to reduce the effects of erosion. Planning and building roads directed towards the west was even more challenging as their courses went against the natural topography. In these areas, construction of bridges was required, some of considerable length and height, and elsewhere cutting back the rocky hillside was necessary in order to secure a width suitable for a vehicular road We estimate that one of bridges over the Helisson River, of pre-Roman date, had a length of 27 m while at the Elliniko of Megali Valtsa the rock was cut vertically over a total length of ca. 150 m and a maximum height of 1.7 m for the construction of a road 4 m wide. Equally impressive is the Roman avenue linking Corinth to Achaia, the straight course of which necessitated bridging numerous rivers and ravines.
Many of these roads were visually controlled by watch towers scattered within Sikyonia. Rectangular, and more rarely circular substantial structures, were rising on conspicuous spots of the countryside, thus guaranteeing visual communication with one another, the forts and, ultimately, with the city itself. Visual inspection of the “straight road” to Phlious was succeeded thanks to at least four towers and two forts which were identified above the left course of the Asopos River. Most of the Sikyonian forts were erected close to the southern borders of the state with one known exception – the fort of Elliniko of Megali Valtsa. This is how we can explain the erection of a fort at Titane, which visually communicated with the tower of Prophitis Elias of Paradeisi to the north and the fort of Kokkinovrachos to the southwest – the latter offering views both on Phlious and Stymphalos. With a surface area of 5,580 m2, a massive wall 2.2 to 2.3 thick, equipped with six towers and a tower at the top of the hill, it is certainly the most important fort of Sikyonia surviving to this day, and deserves to be included in the Permanent Catalogue of the Listed Archaeological Sites and Monuments of Greece, published by the Greek Ministry of Culture. Control of the valley of Klimenti and Kaisari was guaranteed by two forts (Goulas and Agios Konstantinos of Kaisari), and at least two towers (Tsakouthi and Thekriza) while the fort of Elliniko of Megali Valtsa was built at the cross-road of a road coming from Stymphalia and another from Pellene, both directed to Sikyon.
Besides their function as sites for visual inspection of the boundaries and roads of Sikyonia, forts also served as refuge points for the population of the countryside, as in the case of the Kastro of Gonoussa, 2,000 m2 of surface area. Below the Kastro, we located two important settlements (Gkourkioni and Agios Dimitrios) with an artifact surface scatter of 2 and 2.8 ha, respectively, and signs of habitation from Mycenaean times to the Ottoman period.
Out of the 250 archaeological sites that we have mapped and examined in Sikyonia, we identified 148 as representing areas of habitation, with the earliest going back to the Neolithic period and the latest to the 19th century. We observed a certain concentration of prehistoric sites in proximity to the coastal plain (10 out of the 18 sites of this period), where also lies the most important prehistoric settlement site of Sikyonia that we have recorded, namely Litharakia of Krines, with a ceramic surface scatter of ca. 3 ha and an occupation from the Neolithic to the Geometric period. Habitation in Sikyonia followed a rising course from the 6th millennium to the Late Helladic period, and from the Geometric to the Classical period, where it reached its peak.
The Classical period saw the appearance of the largest settlements outside the city (in 12 of those we observed a surface material scatter of over 2 ha), but also a multitude of smaller settlements (scattered over an area between 0.1 and 0.8 ha) which probably represent isolated farmsteads. For the satisfaction of the vital needs of the population, people have now started cultivating even marginal areas, semi-mountainous and usually lying on a slope, and attempted to improve their fertility by constructing retaining walls and other infrastructure works. In later Hellenistic, and less so in Roman times, we witness a shrinkage of settlement sites in the chora of Sikyonia. Recovery will come in Late Roman times, a phenomenon witnessed also in other areas of the Greek world. During this period we observed a tendency for medium and large sites with a corresponding reduction in the number of smaller sites, which suggests a growing preference for communal living. In addition, churches and monasteries now appear in the countryside, a tendency continuing during the Byzantine and post-Byzantine period, with the best example being that of the monastery of Lechova on mount Vesiza.
The reduction of the rural settlement sites in Hellenistic and Roman times may be due to a general demographic crisis or (and) to the concentration of the population in the refounded city – the plateau of Vasiliko. The location and mapping of the visible segments of the ancient walls of Sikyon showed that the entire plateau, ca. 230 ha of surface, was intramuros.