Padirac Cave

The Padirac Chasm or Gouffre de Padirac is a cave located near Gramat, in the Lot département, in France.
Features
The chasm itself is approximately 99 m (325 ft) around its rim with a diameter of approximately 35 metres (115 ft). Visitors descend 75 m via a lift or a staircase before entering the cave system. The cave, at a depth of 103 metres (338 ft), contains a subterranean river system that is partly negotiable by boat. This cave system is regarded as "one of the most extraordinary natural phenomena of the Massif Central".
Formation
The chasm was created at an undetermined point in time when the roof collapsed into a large internal cavern. It is known that the cavern existed in the 3rd century, and was inhabited during the 15th and 16th centuries during which time Potassium nitrate was excavated from the area.
Tourism
The first tourists visited the cave on 1 November 1898; however, the site was...