Gouffre de Proumeyssac, Show cave in Audrix, France

The Gouffre de Proumeyssac is a natural cavity in Audrix, Dordogne, formed in yellow detritic Maastrichtian limestone. It consists mainly of one large chamber 42 metres deep, with galleries, stalactites, stalagmites and monoliths; it is called the "crystal cathedral". A metal walkway with a railing curves above the floor beneath dense clusters of amber and gold stalactites.

In the 18th century a hole in the ground here released vapour that locals took for volcanic smoke, and legend made it the devil's home; a police chief had it bricked over. Many human and animal corpses were thrown in. Gabriel Galou explored the shaft in 1907. Until 1957 the cave was reached only by a 54-metre shaft; a horizontal gallery was later cut for walking access.

The cave is called the "crystal cathedral" for its stalactites, monoliths and stalagmites. Its petrifying fountain coats artisanal pottery in limestone over about a year, and the pieces are then sold. Triangular crystals also occur here, found in only three French caves.

Visitors can reach the cave either by walking through a tunnel or by taking a gondola descent, with the tour lasting around 45 minutes. The route is well set up with lighting and railings, making it accessible to most visitors without special equipment.

Until 1957 the only way in was a 54-metre shaft, descended by gondola; a horizontal tunnel was cut later so visitors could walk in. A modern gondola descent is still offered for an extra fee. The triangular crystals found here occur in only three French caves.