In Besançon, the collapse of a road reveals a vast underground gallery. Studies carried out in recent days have discovered the existence of an incredible underground system.
Rainwater underground was able to release the sediments which contributed to this filling. Droughts and human activities also favor this underground disorder, says hydrogeologist. It will take several weeks, if not months, before this road reopens to traffic, says Pascal Reilé, a fine karst soils connoisseur.