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 Clementinum is a historic complex of buildings in Prague. Until recently the complex hosted the National, University and Technical libraries, the City Library also being located nearby on Mariánské Náměstí. The Technical library and the Municipal library have moved to the Prague National Technical Library at Technická 6 since 2009. It is currently in use as the National Library of the Czech Republic.
Its history dates from the existence of a chapel dedicated to Saint Clement in the 11th century. A Dominican monastery was founded in the medieval period, which was transformed in 1556 to a Jesuit college. In 1622 the Jesuits transferred the library of Charles University to the Klementinum, and the college was merged with the University in 1654. The Jesuits remained until 1773, when the Klementinum was established as an observatory, library, and university by the Empress Maria Theresa of Austria.