Vallorbe Caverns (Grottes de Vallorbe)
The River Orbe carved out these underground chambers upstream from Vallorbe (explored in the 1960s) that are among the most spectacular in Switzerland. After a man-made gallery, you come to a series of lakes and vaults covered with concretions. The point where the river reemerges is nothing short of impressive. Just before the exit is the Fairies' Treasure, a collection of 250 minerals from all over the world.