| Planinska jama (The Planina cave), one of the longest Slovenian
    water caves is a huge tunnel which is the subterranean bed of the Unica
    River. Five hundred meters from the entrance into the cave is a confluence
    of two underground rivers: Pivka River, which flows from Postojna polje
    through Postojnska jama 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 in the pocket valley below the 65 high rocks. The length of the cave is 6.656 m. |