ALG-343, Long Corridor Arch, Tissoukai Area Islet Five. 3 meters high (largest opening, estimated). This is a double arch. Find this arch in one of the numerous parallel corridors of Islet 5. This islet is a serious maze of corridors and explicit directions are impossible. Islet 5 is 1200 meters long and 500 meters wide. Most of these arches can be found after 3 or 4 hours of self exploring.