The underground lake of St-Léonard.

All aboard: paddle across the largest underground lake in Europe.

With a length of over 300 metres, the ‘Lac Souterrain de St-Léonard’ is the largest natural underground lake in Europe and can even be navigated by boat. During a half-hour trip, you will discover a fascinating universe – accompanied by a multilingual guide who will provide additional fun and excitement. The excursion can be perfectly combined with a hike along the Bisse de Clavau, a walk through the old town of Sion or a visit to the nearby castles.