Perperikon megalithic place in Bulgaria

The ancient Thracian city of Perperikon (also Perpericon; Bulgarian: Перперикон, Greek: Περπερικόν) is located in the Eastern Rhodopes, 15 km northeast of the present-day town of Kardzhali, Bulgaria, on a 470 m high rocky hill, which is thought to have been a sacred place. Human activity in the area dates back to 5000 BCE. The first traces of civilization on the hill date from the Bronze Age, while the ceramics found on the place date from the Early Iron Age, as well as the impressive round altar, almost 2 m in diameter