From the car park of the valley of the Gouffre d'Enfer, a path follows the bed of what used to the torrent up to the foot of the dam. It's an impressive spot: the rock faces have been vigorously cut into, to form a dark and narrow bottleneck. The dam was built to supply Saint Étienne with water. You reach the crest via stairs. The volume of water collects at the foot of fir-covered slopes. Fifty metres to the left, there are stairs leading up to a viewpoint looking over Rochetaillée.