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:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.