At the foot of the Refuge du Carro of the Club Alpin Français built in 1925, there is a geological curiosity: two twin lakes, separated by a glacial moraine which are radically different. Lac Blanc has a milky colour due to the muddy waters of the glacier located upstream. Lac Noir is clear, fed by the gneiss outcrops. It’s all about watersheds! Do not disturb this fragile ecosystem by introducing organic matter! The buoys anchored in the middle are used for scientific tracking led by the Federation of Fishermen and the National Park.