Lac Souterrain de Saint-Léonard: Discover Europe's Largest Underground Lake! - Olliechinny
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Lac Souterrain de Saint-Léonard: Discover Europe’s Largest Underground Lake!

Boat exhibit at Lac Souterrain de Saint Léonard

This autumn, we swapped our usual upwards hiking in the mountains…in exchange for a downwards adventure into an UNDERGROUND LAKE in Valais!

About Lac Souterrain de Saint Léonard

Lac Souterrain de Saint-Léonard is located in the heart of the Valais Alps, between Sion and Sierre. It is said to be first discovered in 1943 by Jean-Jacques Pittard, then-president of the Swiss Speleological Society.

Spanning 300 meters in length, 20 meters in width and 10 meters in depth: This is in fact the LARGEST underground lake in Europe! Every year, thousands of people flock from all over Europe to visit this extraordinary nature site.

How to Get to Lac Souterrain de Saint-Léonard

To visit the lake, I would recommend travelling by car. Our car journey took approximately 1.5 hours.

From Geneva – Lausanne: Take the Motorway A1 then A9 exit SION-OST. Cantonal road towards Sierre, St-Léonard (5 km). Note the signpost. Free parking spaces are available about 100m away from the entrance.
parking space at Lac Souterrain de Saint Léonard
entrance of Lac Souterrain du saint Leonard

If you don’t have private transport options, you can still choose to travel by train. From you point of departure, make a change at Gare de Sion and alight at Gare de Saint-Leonard. However, take note that reaching the lake would take a bit of a walk, about 13 minutes away (1.1km) from the train station.

Lac Souterrain de Saint Léonard: The Lake Tour

We were one of the latest to arrive so we boarded the boat the last. But that turned out better, since we got to sit closer to the guide and we could hear the commentary a lot better.

There was a long flight of steps to get down to the bottom of the entrance caves, and there are no lift access: So parents with children or persons with disabilities might want to take note of that.

The two guides spoke in French and German, since it catered to majority on the boat. English is available as well, just let the guide know that you require translation assistance.

Pets were actually not allowed on board, and we were supposed to leave our puppy Kaya alone at the entrance for 30 minutes (the whole duration of the boat tour). But the guide saw how anxious Kaya was, and very kindly allowed him to come on board with us. We were SO grateful for that!

Look at how curious he was looking out towards the waters (He prolly spotted the fishies!)

Inside the caves, the lake is illuminated from place to place, revealing lovely rock walls covered with geological gypsum crystals formed over centuries.

The temperatures inside the caves is consistently around 10-11 degrees, so definitely bring along a warm fleece jacket with you to guard against the cold.

boat tour at Lac Souterrain de Saint Léonard

As the boat quietly sailed through the caves, we peered through the unbelievably crystalline waters. You could even see the sunken boats and fishes swimming underneath!

The main drawback was that we found the tour a tad too short, since it lasted only 30 minutes to and fro.

However, if you would want more out of your experience, you can arrange special events by reservation. For example, there’s options to host a private event with an apéritif and a tasting of Valais specialties. Also, thanks to its grandiose cave acoustics, the lake can also host live music concerts, from classical to contemporary music!

Note: due to COVID-19 restrictions, all visitors are required to wear masks throughout the duration of the boat tour.

Where to Explore After Visiting Lac Souterrain de Saint Léonard

Don’t make the Lac Souterrain de Saint-Leonard your sole purpose for the trip, it’d be such a waste if you leave right after! In fact, the Saint-Leonard commune is surrounded by such beautiful mountain sceneries, and the time after the lake tour would be the perfect opportunity to go on a hike and admire the beauty of the Valais.

Hike Information

We decided on an easy trail that took us about 1.5 hours. We started from the Saint-Leonard town. Walk towards the direction of the church, head up towards the vineyards and then take a detour back to the town.

The trees along the meandering paths were in beautiful hues of yellow and brown, begging to be photographed!

Did you know? The vineyards in the Valais region accounts for one-third of the total wine production in Switzerland. The Pinot Noir is undisputedly the king of Valais, with the white Chassela takes second place.

Our hike coincided with the peak of autumn season, and the vineyards were bursting with life! We even got to pick grapes among the golden fields.

Along the way, we passed some old ladies who were gleefully carrying huge bags of grapes. As they rightly pointed out, tongue-in-cheek: les oiseaux viendront les manger quand même! (If we don’t pick the grapes, the birds will come eat them anyway!)

My friend Maha also discovered a fig tree and squealed that there were so many fruits growing on it! It was my first time tasting fresh ripe figs, straight off the trees. They are so healthy, and absolutely delicious.

lac souterrain de saint léonard pinterest pin

I enjoyed our trip to the underground lake. Apart from our usual weekend adventures up in the mountains or in the bustling Swiss cities so far, this felt like a refreshing change and allowed us to explore a different aspect of Swiss nature.

With a dazzling rock formations to discover underground and a calm, scenic hike amongst the vineyards, I hope that gives you more than enough reason to visit Lac Souterrain de Saint-Léonard and its surrounding region this autumn!

Useful Information

Lac Souterrain de Saint-Léonard
Case postale 75
Rue du Lac 21
1958 Saint-Léonard
Tél. : 027 203 22 66

Admission Prices:

12 CHF for Adults, 5 CHF for children 5-17 years old

Free entry for children below 5 years old

If you are still looking for some inspiration on where to travel next, why not check out my other Swiss travels, such as my recent daytrip to Gruyères and our weekend vacation to Lugano? Be sure to also leave a comment in the section below and let me know about your next adventure this autumn!

We were invited by Lac Souterrain de Saint-Léonard in order to bring you this story. As always, opinions are all my own, and hosts have no editorial influence on articles.

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1 Comment


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