The Cave of Crystals is a horseshoe-shaped cavity in limestone. Its floor is covered with perfectly faceted crystalline blocks. Huge crystal beams jut out from both the blocks and the floor. The caves are accessible today because the mining company's pumping operations keep them clear of water. If the pumping were stopped, the caves would again be submerged in water. The crystals deteriorate in air, so the Naica Project is attempting to visually document the crystals before they deteriorate further.