Lac du Bouchet

It's a lake of volcanic origin located in the Massif Deves (1421 m) between the Loire and Allier, 20 km from Le Puy en Velay.
The water level of the lake is 1205 m above sea level, it is a body of water 28 m deep. Lake is not on top of a mountain, it nevertheless occupies a crater formed during explosions 800 000 years ago, due to meet in-depth hot lava and groundwater or infiltrated from the surface.
The continuous renewal of water is the greatest mystery of the lake. Indeed, its waters are pure, even very pure. Yet there no known source visible, or rivers that could give birth.