Groin Natural Bridges is located in Groin Canyon near the village of Artemare in Ain department of France (about only 1km distant to Cerveyrieu waterfall). Sometimes the bridge opening can be inudated by water flow at high stage. In this case, you have to cross it underwater by a short body immersion. This canyon is a masterpiece of erosional work with a fantastic subterranean atmosphere in the narrow part where you have to swim in total darkness. The canyon houses also 3 other natural Bridges, most of them are siphons and it is virtualy unphotographable. The author has never seen a better spot in this canyoneering experience despite the oppressive ambience inside it.