The lake occupies a structural depression formed during the Würm glaciation.
It is locally nicknamed the 'Lake of the Three Communes' because it touches the borders of Xonrupt-Longemer, Gérardmer, and Renauvoid.
The Vologne River is known for its historical 'pearl mussel' population, which historically brought royal attention to the region's waters.
The site contains specific protected peat bog vegetation zones along its margins.
Water temperatures in mid-summer are generally warmer than other high-altitude lakes in the Vosges due to its relatively shallow average depth.
It serves as a primary flood regulation basin for the Vologne river valley.
Lac de Longemer is a glacial lake located in the Vosges mountains at an altitude of 736 meters. Created by the retreat of the Vologne glacier, it covers 76 hectares and reaches depths of up to 34 meters. The lake is fed by the Vologne River, which flows through the water body before exiting towards the downstream Lac de Retournemer. It is situated within the Ballons des Vosges Regional Natural Park. The site is characterized by steep, forested slopes and granite surrounding terrain. Recreational activities include swimming, pedal boat rentals, and fishing for trout and pike. A marked hiking trail circles the lake, providing direct access to the shoreline and forest periphery. The lake is protected for its local ecosystem and water quality.
The eastern shore along the bridge crossing the Vologne inflow.
Bring non-slip footwear if you plan to walk the trail, as the path can become muddy after rainfall.
Park in designated lots rather than the roadside, as local authorities strictly monitor parking along the main road.
Bring your own supplies, as dining options are limited primarily to the immediate vicinity of the main beach area.
Attempting to swim outside of designated lifeguard-monitored beaches during the high season.
Water sports and beach facilities are available only during the summer season.
Respect the marked swimming zones, do not discard waste in the forest, and observe noise restrictions near nesting areas.
