The source of the Hérisson is at an altitude of 805m, and the river tumbles down the slopes in spectacular waterfalls. It rapidly reaches the Doucier plateau, dropping 280m in 3km. In the gorges, it forms numerous waterfalls, such as the famous Cascade de l'Eventail, and is a superb sight in the rainy season (autumn). After long periods of fine weather, the river can virtually dry up, revealing natural stone steps, giants' cauldrons and multi-storied cave systems. Lots of walks (take waterproof clothing).