L'Arche du Trou Noir (Black Hole Arch) is located close to the Grotto of Trou Noir on the cliff of Grand Bachat near the hamlet of Le Grand Ratz on Chartreuse Regional Natural Park in Isère department of France. Access to the arch and grotto require harness and helmet to go along a rope handline on a narrow passage. The opening has an estimated height of 2.5 meters. IGN topographic map Top 25 issue 3334 west Chartreuse Sud (pleat B1).