Is not known when the original city was built, but it certainly is one of the oldest forts in this region. The Ottomans didn't demolish the Roman mausoleum, instead they built the fortress around it. This, for the major part, allowed for the older remains to survive in relatively good shape until today. Sultan Bayazid II built the present fortifications in the form of an irregular pentagon with the maximum length of and width of , designed to withstand cannon warfare. The city consists of 5 towers at four levels (three floors and the ground level), three on the east and two on the western rampart. Apart from the place, where the fortress is entered, there are four corner towers. The side towards and fort are surrounded by a low wall and wide dry moat in front of it. City entrance is at the keep tower ("donžon"), which is located in the southwestern side of the fort. The towers have different bases, but are projected in regular pattern and built in the similar architectural conception. On the first floors of each tower there were cannon embrasures. The walls are thick. In order to prevent easy capture of the fortress, the upper floors could be reached only via the each tower's gate or the outer stairs.