Gouffre Jean-Bernard

Further explorations in the following year reached the main drain, or master cave, of the system at a depth of −210 m (−690 ft).

[a] This was further explored downstream in 1965 and 1966, reaching the base of a wet shaft, the Puits des Affreux, at −380 m (−1,250 ft).

A major expedition in 1969, attended by many French cavers, reached a sump at −623 metres (−2,044 ft).

More recent explorations have increased the depth to 1,612 m (5,289 ft),[3][4][5] making it the seventh deepest cave known in the world.

[6] The Gouffre Jean Bernard is located in a synclinal valley (Vallon des Chambres).