The warm waters of Pré-Saint-Didier flow out from the heart of the mountain at a temperature of around 37° C. The water of Pré-Saint-Didier is a saline-acidulous-arsenious-ferruginous water with moderate radioactivity. It also contains silica, arsenicated acids, iron oxide and calcium carbonate.
The warm thermal waters were used for many years to treat rheumatic and muscular disorders, as well as skin ailments and blood circulation problems. They were also famous for being relaxing, for possessing tonic and fortifying properties and for soothing both the body and the mind.