As we know, Slovenia is a land of many fascinating caves, but only one of them is the longest water cave in the country. This honour goes to Planina cave, just a short drive northeast of Postojna. In this buried wonderland two underground rivers meet (rivers Pivka and Rak), making this one of the largest confluences of subterranean rivers in Europe. The entrance to the cave may be a bit imposing, and it is far from the safest cave, so special visits are available only through appointment.