The granite ridge of the Reisberg separates Lac Blanc (White Lake) from Lac Noir (Black Lake). The two stretches of water communicate through a pumping system that regulates their level. Lac Noir (Black Lake) is nestled at the bottom of a glacial cirque of high granite cliffs. Its waters' floor consists of black peat bogs, which gives it its deep color. Surrounded by tall firs and spruces, the lake's dark decor seduced directors Jean-Pierre Mocky and Régis Wargnier for the shooting of three movies.