Behestan Castle

Behestan castle, also known as Ancient Castle Behestan, Ghale behestan, Behestan Rock Castle is one of 20 castles located in Mahneshan ancient city in Zanjan province, probably is the most unique one because it is built inside of a 250 meter Conglomerate mount by delving it instead of building the castle over it.
Experts believe at first it was used during Median or Achaemenian tribes era, but definitely current castle dates back to middle ages of Islamic era in Iran (11th century AD).