This natural tunnel is located above the narrow gorges of Combe d'Oyans near the hamlet of Les Ducs on Vercors massif in Drôme department of France. The tunnel has an estimated depht of 100 meters. IGN topographic map Top 25 number 3136 east Combe Laval (pleat E1).
On August 23 2017, Pascal Sombardier lead a trip to Grand Tunnel d'Oyans and the
natural arch both located at the middle of a sheer cliff above the little canyon of Oyans (Combe d'Oyans). Participants was Cathy and Raf, Bruno, the author and our awesome leader Pascal Sombardier. Access to these two natural treasors require to rappel four time nearly 160 meters (500 feet) on a vertical cliff with a rope pendulum from a free rappel to enters into the span of the arch (the gate of the tunnel). The Grand Tunnel d'Oyans begins immediately below the opening of the arch and can be reach by a rappel of 20 meters.
