Chailles Natural Bridge is a very old pothole bridge (the biggest that author has ever seen in a canyon) located on Gorges de Chailles near the village of "Pont-de-Beauvoisin" in Isere-Savoie department of France. To visit the bridge, you have to descend this Dante's canyon using canyoneering material and swims Guiers River most of the time on deep water (nearly 1km). The major difficulty is to rope down a dangerous 10 meters waterfall just past the natual bridge. A very impressive spot.