The 1km-long cave, discovered in 1948, contains many stalactites and stalagmites as well as broad swaths of melted calcite in unusual shapes evoking cascades, huge organs and draperies (in the Matterhorn, Great Organ, Hindu Temple and Gallery of Wonders rooms). The tour includes a 250m boat ride on an underground river formed by water from the Adour which flows into a goule on the right bank of the river at Campan, and comes back out in the park of Médous castle.