Diocletianopolis, Thrace

Diocletianopolis was a major Roman city in Thrace, now the town of Hisarya in central Bulgaria. The site has been inhabited since around 6000 BC, drawn by its hot mineral springs. Under Rome, the settlement was called Augusta and became one of Thrace's three most important cities. Emperor Septimius Severus visited, and in 293 AD, Diocletian renamed it after himself. Impressive 4th-century fortification walls form a 2.3 km circuit with multiple gates, including the distinctive double-projection "Camel Gate" on the south side. The city featured elaborate thermal baths fed by natural hot springs. After the collapse of the northern frontier, Diocletianopolis was destroyed during the Slavic migrations by the early 7th century.