A natural well leads to this admirable swallow-hole. The tour starts in the Great Chamber or Tomb Chamber. The bones of animals (bison, deer and bears) indicate that it was occupied by humans in very ancient times. The cave displays a wide diversity of colours and shapes (bunches of grapes, disks, etc.). The Diamond chamber is the culminating point of the tour; it is 130 m below ground level, glistening with thousands of crystals.