The Škocjan Caves (Škocjanske jame) are a unique natural phenomenon, the creation of the Reka River. The Reka River springs from below the Snežnik plateau and flows some fifty-five kilometres on the surface. After reaching the Karst, that is the limestone surface, the river not only deepens its riverbed through erosion, but also by means of corrosion – it dissolves the limestone. The Reka River blind valley is the largest in Slovenia. In the distant past, probably in the Early Pleistocene, that is a few hundred thousand years ago, the ceiling of the cave collapsed some 200 metres from the sinks; as a result, the collapse dolines Velika dolina (up to 165 metres deep) and Mala dolina (120 metres) were created, separated by a natural bridge, a remnant of the original cave ceiling. Above the caves, between the wall above the sink and the walls of Mala dolina, lies the village of Škocjan. Close to the houses, there is another entrance to the underground, a ninety-metre-deep abyss called Okroglica, which ends just above the underground Reka River. At the bottom of Velika dolina, the Reka River finally disappears underground and resurfaces again thirty-four kilometres away at the springs of the Timava River, not far from the Adriatic coast.
Škocjan Caves and karst above them in the area of the Škocjan Caves Park, are on the edge of the Classical Kras (Karst). They are in the close contact with imperable flysch and permeable limestone, in the so-called contact karst. Caves are composed of several parts: the greater part is flooded, but upstream are also dry caves. Due to their exceptional significance, the Škocjan Caves were entered on UNESCO’s list of natural and cultural world heritage sites in 1986. International scientific circles have thus acknowledged the importance of the Caves as one of the natural treasures of planet Earth. Škocjan Caves are also the first underground wetland in the list of RAMSAR and included as Karst biosphere reserve in the program MAB - Man and Biosphere. The importance of Škocjanske caves is in their position, they act as a sink and they are part of the Karst aquifer, they are a unique heritage, which includes also rich groundwater communities.
