Perperikon is the most widely famous archaeological site in the Eastern Rhodopes. It is an enormous religious complex of a Thracian sanctuary, built upon a peak near the village of Gorna Krepost (Upper Fortress). A passage with a length of 90 m, width of 4 m and height of 6-8 m was carved into the solid rock, leading up to the complex. It has an area of over 20 000 square meters, and inside you can see hundreds of carved graves, stairs, ritual rooms, altars, niches, columns, streets, water reservoirs, and many other openings and signs with yet unrevealed purposes. When you stand at the top of the sanctuary, you will be amazed by its size, and by the extreme precision in the work of carving. According to the latest researches, the first signs of human activity date back from 7 milleniums ago. Due to the strategic location, there used to be a medieval fortress at Perperikon. The fortress held the administrative center of the Ahrida Region. There is not much left of the fortress today: only part of the wall, previously surrounding the whole peak, and one of the defensive towers with a height of 15 m.