Caves and potholes

4,500 caves or chasms, which in this region often go by the name of 'baumes' or 'puits'.

Many of these cavities are known to sports lovers, such as the Verneau caves in the Lison valley, which are considered to form the world's longest post-siphon network (28,000 m). In Franche-Comté, to reach heaven the pot-holers head downwards.

Many of the caves are also tourist attractions.
Caves, sources or resurgences to visit to discover the underground rivers at Les Planches near Arbois, at Baume-les-Messieurs, at Osselle; a chasm which can be descended very easily at Poudrey close to Besançon; the miraculous chapel cave of Remonot downstream of Pontarlier.

Travelling to the centre of the earth in Franche-Comté is also a way of going back in time: these caves were inhabited by the first prehistoric men known to have lived in France, such as in Vergranne, or were used as refuges during invasions, hiding places for the Comtois resistants to the French invasion in the 17th century, and for the partisans in the Second World War.

A land of legends, also, of course: the cave of treasure, the den of the wyvern… Last of all, they are the natural habitat of the bats which proliferate in Franche-Comté (indeed, almost all the species listed in France are to be found here) thanks to the diversity of the cave networks. The riches hidden underground are not necessarily what you might first imagine.