The subterranean lake of St-Leonard

The largest underground lake of Europe

The subterranean lake of St-Leonard is located in Switzerland, along the Rhone valley, between Sion and Sierre in the heart of the Swiss Alps.
With a length of around 300 meters this is the largest natural underground lake in Europe which can be explored by boat.
During a 30 minute boat trip on the crystal clear water, you will enjoy the peace of this amazing place while your guide explains all sorts of fascinating details about the origin and the history of the underground lake.

Practical information

Duration of the tour is around 30 minutes and the temperature in the cave is 15 Celsius.
Tours start all day long, every 20 to 40 minutes.
No prior booking needed for individual travelers. Groups over 20 people might book in advance.
In the morning, the first tour starts about 20 minutes after the first visitors arrive.
All tours are guided tours on a boat with explanations in English, French and German.
Other languages on request depending on availability.
Pictures without flash allowed. It is not possible to access the cave on foot. Swimming and diving are not permitted.


Lac Souterrain de Saint-Léonard
Case postale 75
Rue du Lac 21
1958 Saint-Léonard

Tel : +41 27 203 22 66


Adults (from 16)
CHF 10.-
Children (5-15)
CHF 6.-
Children (0-4)

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