Discovered in 1953, La Verna is 194m high and 245m in diameter, making it the third-largest known cave in the world: it could hold Paris's Notre-Dame ten times over. As you visit this chamber, into which a river disappears, you will learn about the history of the pioneers who, in 1950, began exploring the karst of La Pierre-St-Martin. In this way, 456km of underground networks and 1 600 chasms, hollowed out by 13 rivers, have been explored.