The ruins of the Osule castle lie on the hill of the same name about 1 km north-west of the small village Vitějovice.

The history of the castle dates back to the 13th century. It was founded here by King Premysl Ottakar II near the trade route called Zlatá Stezka (Golden Path). The owners of the castle changed several times in the 14th century and the building was never completed. After the completion of the neighbouring Helfenburk castle, built by the Rožmberks near the small town Bavorov, the Osule castle was destroyed.

The castle was 15 m wide and about 50 m long and it had an oval layout. The remains of the walls have been preserved up till present.

Osule can be found on the blue marked path leading from the village Vitějovice (1.5 km).