Asen’s Fortress is a medieval structure built into the rocky ridge of the Rhodope mountains over the Asenitsa river. This strategic place was first the location of a Thracian fortress, later used by the Romans, the Byzantines, and eventually the Bulgarians. It was renovated during the 13th century during the reign of Ivan Asen II to be used as a line of defense against the Latin Empire. It is destroyed in 1410 by the invading Ottoman armies. Today, the fortress lies in ruins, with a small church functioning within what remains of its walls.