Planinska jama (The Planina cave), one of the longest Slovenian water caves (>6,5 km), is a huge gallery of the subterranean Unica River. Five hundred meters from the entrance into the cave, a confluence of two underground rivers can be observed: Pivka River, which flows from Postojna cave, and Rak River, which flows from Rakov Skocjan. This is the largest confluence of subterranean rivers in Europe. Entrance into the cave is on the southwestern part of Planina polje. A visit of the cave is generally only possible with local guides - which provide the boats necessary for a visit. At the end of the active river, an old dry gallery is worth visiting - the so called "paradise" - coming up with very beautiful formations.
Conclusion: definitely worth visiting!