Lake Sai Bat Cave

Lake Sai Bat Cave is a lava tube system running approximately 386 meters underground with multiple chambers throughout its passages. The cave displays various solidified lava formations and mineral deposits created by ancient volcanic flows.

Mount Fuji's volcanic eruption between 864 and 866 created this underground tunnel network through flowing lava streams. The cave received official designation as a Natural Monument of Japan in 1929.

The cave received Natural Monument of Japan status in 1929, recognizing its geological importance and role in preserving local bat populations.

Visitors must wear protective helmets when exploring the cave for safety during the passage through tight spaces and chambers. The cave is accessible between March and November, giving you several months to plan your visit.

Five different bat species inhabit this cave system, including the Greater horseshoe bat and Japanese long-eared bat. These creatures use the space as a natural shelter, making it an important wildlife sanctuary.

Location: Fujikawaguchiko

GPS coordinates: 35.49311,138.67286

Latest update: December 10, 2025 15:50