Blagaj Fortress or Old Town of Blagaj, locally known as Stjepan-grad , or Stipan-grad, in classical times Bona, is a town-fortress complex near the town of Blagaj, Bosnia and Herzegovina. The old Blagaj Fort was built on a high, inaccessible karst hill, at an elevation of 310 metres above sea level and 266 metres above the source of the river Buna.