The Fortress of Perperikon is located 20 kilometres north-east of the town of Kardjali in Southern Bulgaria. This archaeological ensemble is typical for its rich stratigraphy, with the earliest discovered strata dating to the Iron Age. The fortification, which was built in antiquity, had been continuously developed and reconstructed through the Middle Ages: documents from the 13th and 14th centuries mention it under the name of Hyperperikon. The Fortress is located on a broad and not very high rocky hill, with the citadel erected on the summit. The site of the castle is immediately below, and the substructure is located on the lower flat terrace. In the valley, beneath the Fortress, the remains of a mediaeval monastery were discovered, which, according to existing data, had been an important religious-worship and military centre. Perperikon was built some 7 000 years ago Recently, the excavations at the site revealed that the grandiose religious centre Perperikon was built some 3,500 years ago.