Enjoy a 5-hour guided tour to the incredible Postojna Cave with a photo stop at the largest cave castle in the world, Predjama Castle. Explore the extensive Postojna cave system with cave passages over 20 kilometers (12 miles) in length on an unforgettable underground train ride.  The Postojna Cave system is the largest known cave system in the country and the second-largest accessible to visitors in the world. Postojna Caves lie under the slopes of a broad karstic limestone plateau on the eastern fringes of the Postojna basin and offer a unique opportunity to spot some of the local wildlife that lives in the cave. Just ten minutes far away from Postojna caves is Predjama castle, another jewel of the Karst region. Predjama Castle pressed into a huge cavern hollowed out of the high, flat rock face, above the karstic swallow hole of the Lokva stream. The castle boasts as the largest cave castle in the world. It is a truly unique sight and will make for an unforgettable sight, not to mention a great photo opportunity.