Postojna jama (cave) is a 24,340 m long karst cave system near Postojna, southwestern Slovenia. It is the second-longest cave system in the country as well as one of its top tourism sites. The caves were created by the Pivka River. Here, Pivka jama (cave) and the Black jama (cave) are the final two caves along the subterranean Pivka River before the river finally disappears and resurfaces in the Planina jama (cave).
