On a clear day, the sky is reflected in the crystal-clear water of Lake Pavin and gives it a particularly pronounced midnight blue color. On a cloudy day, its deep waters appear dark and threatening, hence its name from the Latin pavens, which means appalling. The lake born from the explosive encounter of lava and water is the subject of numerous legends fueled by unusual manifestations. The large bubbles of methane produced by the decomposition of plants remnants that sometimes rise to the surface have thus long been considered as diabolical manifestations at the gates of hell.