Postojna cave, in Slovenian language called “Postojnska jama” is second greatest Slovenian tourist attraction (first place belongs to Bled). Postojna cave is a name for a system of caves, typical for unique Slovenian landscape called Karst (Kras). The caves were hollowed out by the river Pivka. Postojna cave is with its 20.570 m also the longest cave system known in Slovenia and the most visited tourist cave in Europe. Postojna cave was opened to the public in 1819.