What is "kurvingrad"

Kurvingrad ( Serbian Cyrillic: Курвинград) (Whoretown) or Koprijan is the fortress which rises above the South Morava river, 11 km south of the town of Niš, respectively located in the village of Doljevac. It is assumed that this is the Medieval Koprijan, a town at the foot of the remains of a large settlement from the time of Antiquity, so that alone Citadel has millennium continuity of existence. Today, there are remains of fortifications, but they are not sufficiently studied.