Ostrožac is one of Bosnia's most photogenic castles, a spooky Gothic place high above the Una Valley, up 3km of hairpins towards Cazin. There's plenty to explore from various epochs, ramparts to walk, towers to climb and a manor house on the verge of collapse that all add to the thrill (and danger) of poking about. Off-season you might have to call the caretaker to get in, but it's only officially closed if it's snowing.
First mentioned in 1286, Ostrožac capitulated to Turkish forces in 1577, was swiftly regained then lost again by 1579. It was the seat of local captains for 250 years and was restored with its current picture-book look around 1905. The central lawn contains an interesting sculpture garden, founded in 1969.