Open to the public for a quarter of a century, the Vallorbe Caves in the Jura mountains of the Canton of Vaud offer a fascinating spectacle of mineral beauty enhanced by lighting.For millions of years the limestone layers have been eroded by the Orbe, a river that flows underground before flowing back from the rock as a spring whose most faithful witnesses are the caves of Vallorbe.Inside these cavities, which are among the most beautiful in Europe, there is a mineral exhibition, "Le Trésor des Fées", which includes a collection of 250 minerals from all over the world under four domes dug into the rock.