Caves of Neptune (or of Adujoir)
The River Eau Noire, so called because of black rock lining its bed, disappears into the Adugeoir chasm before resurfacing near Nismes. Visitors can see three tiers of galleries with fine concretions. The Eau Noire has not flowed through the upper gallery for centuries but floods the middle gallery when water levels rise. There are small boat rides along the underground river in the lower gallery which enable visitors to see a spectacular waterfall and a Son et Lumière show at the end of the trip.