The cave most frequented on the island is the easily accessible Command Hill Cave, a lava tube found close to the airstrip in the South-West of the island. This approximately 100 metre long, 5 m wide and 3 m high tunnel can be accessed via a steep 10 m descent. Near Sisters Peak in the northern part of the island there are several impressive fossil fumaroles. While the entrance to one of these has a ladder, they are hard to explore, being humid and having extreme temperatures of greater than 30°C.