The mediaeval fortress of Vjenčac was built as the Nevesinje Governor headquarters and later on it was also the seat of the prince. The popular name of this locality is Knežača or Grad. It is located southeast of the urban part of the town, while its material remains are visible in the form of thick walls of a military fort because, due to its thickness and massiveness, it has resisted all misfortunes to date. The building lost its importance with the arrival of the Turks.
Besides Vjenčac, Biograd, Zaborani and Postolja (Postoljani) are also mentioned as the seats of the dukes and governors of Nevesinje. Biograd, together with Podgrađe, is mentioned in historical documents in 1281 as an important trading post with an open market during the reign of Herzog Stjepan and his sons. It is referred to as Fort Kastel in 1454, as Herzog Šćepan’s estate. Most probably, a Roman settlement in the same place, located on the said Roman road that ran from the coast (Metković) to Sarajevo and Foča.