Hölloch

With a length of more than 200 kilometers, Hölloch is regarded one of the world's most extensive cave systems. You can explore and experience a world you've never seen or imagined with daylight tours and adventurous expeditions.

You can't seem to get away from the cave's allure. It's simply incredible how much elemental energy nature used to construct such rock structures over a million years.

A party led by Alois Ulrich conducted the first scientific exploration of the cave in 1875. Later expeditions in the 1950s led by Alfred Bögli, a pioneer of speleology, were able to explore a substantial portion of the cave.

The cave's investigated length increased from 25 kilometers (16 miles) in 1952 to 100 kilometers (62 miles) by 1968. It was the first cave in the world with an examined length of 100 kilometers, and it was thought to be the world's largest cave system until the Flint Ridge Cave System was linked to the Mammoth Cave System in 1972.

Despite this, the Hölloch was explored further, and by 1976, it had been mapped to be around 130 km (81 mi) long.

Location: Canton of Schwyz