Caves of Vallorbe

150 million years ago, the area was covered by a sea and resembled an island landscape. In the following 10 million years, about 200 meters of limestone were deposited, which serve as the basis for the formations in the cave. In the next 120 million years, additional layers, such as sandstone, marl, and clay, were added. About seven million years ago, the sea finally retreated due to tectonic changes. The basic conditions for the caves of Vallorbe had been created.

Toward the end of the 19th century, water coloring demonstrated a connection from Lake Brenet to the lower Orbe spring. However, a diving attempt into the cave system was unsuccessful due to a lack of technical equipment. It was not until 1961 that three divers managed to explore 140 meters deep into the cave system during five dives. In 1964, two more divers discovered a dry gallery above the “Lake of Silence.” By 1966, research conducted by another three-member diving team had already revealed several hundred meters of dry galleries.

Wikipedia