Nicknamed the thousand reflections mirror because of its changing brightness, the lake of Longemer is a natural pool of glacial origin. At the foot of the Vosges mountain, it is crossed by the Vologne river, at an altitude of 2,400 ft (736 m). It stretches over 187 acres (76 ha), heading towards the valley. The lake of Longemer is a well-preserved Natura 2 000 classified site and one of the three lakes in the Lakes valley. It is also part of the Regional Natural Park of Ballons des Vosges.