The karst caves lie south of Trebnje, on the north side of the slope of Vrhtrebnje in the vicinity of the Trebnje Castle. Velika and Mala jama Caves represent part of a former extensive cave system. Although the origin of the caves is closely connected, the caves differ dramatically. Part of the slope of Vrhtrebnje is mainly beech forest and in the lower part it is mostly rocky. Below the caves at the edge of the forest is the Grajski Studenec or well. Velika jama Cave is 142 metres long. The height above sea level is 432 metres. The peculiarity of the Trebnje caves is that besides other animals, bats also take refuge in them.