When we went to the Matterhorn, we saw the geology of Switzerland firsthand. On the way back, our quads were sore and we weren’t up to another big hike. As a result, we decided to see the underground lake at St. Leonard in Valais. It was touristy, a bit cheesy, another geology lesson and cooler than I am making it sound.
The lake was discovered in 1943, during a the search for water in a drought.* In 1946 an earthquake opened some more fissures that lowered the water-level. This made it accessible. We entered down the stairs and climbed into these large rowboats. Sorry if the pictures are blurry. The low light and the movement of the boat (and the other 41 people on it), made them challenging to take. They definitely do not do its beauty justice.
The water in Switzerland’s lakes is lovely and crystal clear. The water in this cave is even more so. It is a constant at 11 °C (52 °F) and it is always 15 °C (59 °F).
How can there be fish in this lake you ask? So did we. They are Rainbow Trout. They have no natural food source and no predators so they were HUGE. The guide feeds them from the rowboat. They were pretty cool to see up close. I’m not sure who was more into them, the kids in the boat or their parents.
The lake was closed from 2000 to 2003, to improve the cave’s stability. Clearly, they put in tons of ceiling support. If I remember correctly, each side of the cave is a different type of stone and the ceiling is a third. Unfortunately, that one is softer (I don’t want to give you the wrong type so I won’t name it).
*St. Leonard lies in an area of Valais that is the sunniest part of Switzerland.