The Fosse Dionne is a karst spring in the French municipality of Tonnerre in the Yonne department of the Bourgogne-Franche-Comté region.
The spring pot forms a deep pool that is fed by an underground passage. The adjoining cave system has been explored up to a length of 370 m, but leads even deeper into the massif.
Fosse Dionne is notable because of its average daily flow of 311 liters per second, and because its origin has not yet been revealed.
Access : Coordinates: 47.85654, 3.970565 /
- La Fosse Dionne” is a bottomless pit. Despite many attempts, divers were unable to determine its depth.
- The toponym Dionne is said to be derived from the name of the Celtic goddess Divona.
Go next : Tonnerre, a French small city on the Burgundy Canal in the department of Yonne.