Kurvingrad
Doljevac, Serbia
Kurvingrad (Serbian Cyrillic, lit. "Whoretown") or Koprijan, is a ruined fortress which sits above the town of Doljevac on the South Morava river, 11 km south of the town of Niš. The ruins are all that remain of the medieval town of Koprijan from the time of Classical antiquity; the fortress is over a thousand years old. Today, fortifications remain, but have not been substantially studied.
Fort data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).