Postojna Cave is a breathtaking site, known for its uniqueness, complexity and beauty. It is the only cave in Europe with a two-way railway specifically designed for sightseeing. Marvel at the cave's beautiful formations and natural galleries. The caves are also home to the endemic olm, the largest trogloditic amphibian in the world. The tour through the caves includes an aquarium with some olms in it. Just 9 kilometers from Postojna Cave is Predjama Castle, a Renaissance castle built within a cave mouth. In 1570, the current castle was built in the Renaissance style, pressed next to a vertical cliff under the original medieval fortification. The castle has remained in this form, virtually unchanged, to the present day. You can learn about the history of the castle and its use as a location in several films in the castle's museum.