Saiko Bat Cave

This 350-meter lava tube beneath the Aokigahara forest formed when the outer shell of a lava flow cooled and hardened while molten rock continued moving through the interior, leaving a hollow shell with branching passages. Four bat species hibernate here in winter. Unlike the nearby Ice Cave and Wind Cave, which stay cold year-round, the Bat Cave is cool in summer and warm in winter, making it ideal for hibernation. Depending on the route you take, some crawling is required. Helmets are available at the entrance. Exploring takes about 20 to 30 minutes, with lava stalactites and rope-like formations visible along the way, though encountering bats during daytime visits is rare.