The River Orbe created a fascinating cave system at the Vaudois town of Vallorbe. The tour leads visitors along the subterranean course of the Orbe (an outflow from the Vallée de Joux), passing by stalactites, stalagmites, drip-stone formations, columns and galleries. Once upon a time fairies that charmed young men were supposed to have lived here.
The Vaudoise town of Vallorbe lies in a valley basin of the river Orbe, directly on the French border. An inconspicuous chalet is nestled against the slope above Vallorbe. It is the disguised entrance to the fortress "Pré-Giroud".