The Abime de Bramabiau is a river cave on the Causse Noir in the Gard department. It is one of the few tours in Europe that attracts cavers and canyonists alike! The entire system is just over 10 km long, with only one part - the active river course - being traversed at the through trip. Large parts of the higher levels are developed as show caves and it is a bit strange to walk through the stream among the groups of tourists.
You have to get a permit from the show cave a few days before you go through and register at reception - but the operators are extremely friendly! We are in France!
Incidentally, the Abime de Bramabiau is a milestone in French cave exploration: Eduard Alfred Martel began his research here back in 1884!
