Old Town Ostrovica

Stari grad Ostrovica is a large fortification on a steep hill above the left bank of the Una River near the settlement of Ostrovica, close to Kulen Vakuf in the municipality of Bihać. Located within Una National Park, the fortress contains at least three historical layers: a prehistoric hillfort, a medieval town from the 15th century, and an expanded Ottoman fortification.

In the Middle Ages, it was owned by the Kurjakovići (Karlovići), Frankopani, Juraj Mikulčić, and Ivan Keglević. It fell under Ottoman rule in December 1523, and until 1878 a military garrison was permanently stationed there. The Ottomans expanded and strengthened it — especially during the reign of Sultan Ahmed I in the early 17th century — so the walls reached dimensions of 117 × 83 meters, with a height of up to 10 m, four towers, and two bastions. It was the seat of the Stara Ostrovica Captaincy, whose captains came from the Bosnian bey family Kulenović. It has been declared a national monument of Bosnia and Herzegovina.