Dated from Late Antiquity (4th century). It is located on the hill Asara. This fortress was formed as one of the largest and oldest cities in northern Thrace, existed from the 4th century until the early 13th century. It has strong walls, around three meters thick. The entrance to the castle is from the north. During excavations of the fortress were found underground tunnels. Legend says it that this was the residence of the last Roman emperors. In the dungeons of the castle they hid their treasures.