The castle first mentioned in the year 1228 as Gräcz. It is situated in the village Gradac in Bela krajina. In the beginning, it was probably a stronghold against the Turks. The castle stands in a well-protected area of the river Lahinja. It has been declared a national cultural heritage landmark of Slovenia.

In the 17th century, the Gusičs had a magnificent park created along the river next to the castle. Its most remarkable feature was a tree-lined promenade with spruce and plane trees. The 19th and the 20th centuries saw another succession of owners. Among them was Franz Friedau, who built a foundry in Gradac, bringing the town into the industrial age. A wooden bridge connects the castle to the area where the foundry once stood. During World War II, the castle served as a field hospital. After the estate was nationalized by the Communist authorities, the park was neglected. In recent years, what remains of the park is registered as a protected area, a move designed to prevent its complete destruction until a permanent owner is found.