On the outskirts of Alexandroupoli, close to the village of Avantas, lie the medieval castles of Avantas and Potamos. Three different historic eras coexist on those walls, namely the Mycenaean, Classical and the Byzantine era. Both these castles supervised the field and controlled the passages towards the plains of Komotini and inland of the Rodopi mountain range.
Both constructions date to the second half of the 13th century or the first half of the 14th and they are both erected next to streams and on top of steep hills. The Avantas castle is shaped with a simple transverse wall that severs any access to the slope and the peak of the hill. In Potamos the castle has 3 towers that form an internal enclosure and a further external one.
Avantas castle consists of a wall of approximately 140 meters, parallel to the contours and a second, about 40 meters, almost perpendicular to it. The fortified area is of a generally oblique rectangular shape and is slightly less than 1 hectare. The fortification is developed on the slope from which it is possible to rise on the hill, while the rest is not protected by walls because the rough terrain is enough.The fortification was reinforced by four rectangular towers. There were two gates: one at the end of the wall protected by a tower and one in the middle of the wall, between two towers. There are no architectural remains, which might testify residential occupation. The oldest construction elements are some massive domes that have been used in various parts of the fortification which might indicate an older fortification.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.