The St-Léonard underground lake

The mysterious cavern was discovered in 1943 by Jean-Jacques Pittard, but the lake was not open to the public until 1949. The St-Leonard underground lake is the largest of its kind in Europe: it is 300 meters long and 20 meters wide. The boat trip to the lake lasts over half an hour and can accommodate up to 40 people (commentary is available in several languages). A delightful planted terrace with a small children’s playground plus a brand-new educational area, with info on how the cavern and the Alps were formed, invite you to linger.