Saiko Bat Hole

This lava cave is located near Lake Saiko, one of the Fuji Five Lakes, and is known as a habitat of bats.

With a total length of 386.5 meters, it is one of the largest among the many lava tubes at the foot of Mt.
It is designated as a national natural monument.

Formation of the cave
Fuji erupted in 800 and 864, lava flows covered the area from Lake Motosuko to Lake Nishiko, which used to be one vast lake, and formed the lava cave.

Because the cave is located near the end of the filled lake, when a large volume of lava flowed into the lake, it was replenished with gaseous water from the boiling lake water, resulting in a complex three-dimensional, labyrinthine structure with multiple interconnected cavities.

The cave has many unique lava dome, lava rope, and lava shelf shapes that were formed when the magma solidified.

Bats
Unlike other lava tubes at the foot of Mt.

Because anyone could freely enter the cave, the bats in this cave were temporarily on the verge of extinction, and to protect them, a protective fence with iron grating was installed at the cave entrance and exit to restrict entry.

To protect the bats, wooden fences were erected at the entrance and exit of the cave and entry was restricted. The two areas at the far end of the cave were opened to the public as bat protection areas.

During the winter season from December 1 to March 19 of the following year, public access to the caves is prohibited to protect the bats.

Bats are gradually returning to the area as a result of conservation efforts.

Sea of Trees
The northeastern edge of the Aokigahara Sea of Trees, which stretches along the northwestern foot of Mt. Fuji, is located in a deep virgin forest that is dark even in the daytime and designated as a special area of Fuji-Hakone-Izu National Park.
The dense growth of trees prevents sunlight from penetrating under the trees, and the ground is almost entirely covered with mosses.

The forest was formed on top of the lava flow from the eruption of Mt.
The floor appears to be soft mud, but it is hardened lava.

Nishiko Nature Center
It has a kunimasu exhibit hall and a gallery about Mt. Fuji and the Aokigahara Sea of Trees.