Four enormous chambers, home to transparent underground pools, succeed one another over a distance of 2km. The marine origins of the caves seem unquestionable but the French speleologist Édouard Martel who first explored them in 1896, believed that infiltration alone was responsible for the cavities and large numbers of concretions. The roofs are the most amazing feature and covered in an amazing web of countless pointed icicles. The vast chamber in which Lago Martel lies has been converted into a kind of concert hall where music is played.