The Gouffre Berger is a French cave discovered on 24 May 1953 by Joseph Berger, Bouvet, Ruiz de Arcaute and Marc Jouffrey. From 1953 to 1963, it was regarded as the deepest cave in the world at −1,122 metres, relinquishing this title to the previous contender, Pierre Saint Martin, in 1964, after further exploration. The Gouffre Berger is now ranked 37th deepest cave in the world, and the 4th in France.
To return from the bottom of the cave back to the surface can take between 15 and 30 hours, without long breaks.
Wikipedia https://en.wikipedia.org/wiki/Gouffre_Berger
Address 38360, France
Coordinates 45°13'9.322" N 5°36'17.448" E