The glacial cirques of lac Noir (Black lake) and lac Blanc (White lake) are part of the Two Lakes Biological Reserve. They constitute a biologically rich group, with many endemic and rare species from the Vosges mountains. The Black lake is surrounded by trees such as the mugo pine, a variety introduced during the German occupation. Beech groves mingle there, punier as the altitude increases. There are also northern lake species such as the lake quillwort and the small water-lily.