ALG-371, Air Vent Arch, North Idou Maze Area. 5 meter span (estimated). Between ALG-369 (Huge Boulder Arch) and ALG-370 (Home Arch), walk inside a narrow corridor southwest for 150 meters to the arch located on the left. A similar arch is located opposite to this arch on the other side of the corridor. It is very hard to photograph each arch in ideal lighting and have a decent picture in these dark corridors. This is why some arches are not shown here. It is not because those arches are uninteresting (far from it).