🇫🇷France, Gouffre Berger cave
Until 1963, the deepest cave in the world was considered to be the Gouffre Berger cave located in the French Alps. Discovered in 1953 by Joseph Berger, Goufr Berger became the first cave on the planet in which researchers descended to a depth of more than one kilometer.
The Gufr Berger cave system is complex and is considered one of the most dangerous. The base of the walls of the Gufr Berge cave is porous limestone, which is destroyed by heavy rains and floods. It was he who caused the death of the researchers who descended into the cave. In addition, because of the difficult transitions, cavers who have sunk to the bottom of the cave may need from 15 to 30 hours to rise to the surface.