Nakajimadai is a forest where giant Japanese beech (Fagus crenata) and mizunara oak (Quercus crispula) trees that have survived a harsh natural environment grow together. The walking trail through the forest is about 5 km long, and most of the path is a wooden walkway. Walking along the path, visitors will find Japanese beech trees of various shapes, including “Agariko-daiō,” which has been selected by the Forestry Agency as one of Japan’s 100 Giants of the Forest. Its name combines “great king” and “agariko,” which refers to the strange rising shape of its branches.

After the sector collapse of Mt. Chōkai about 2,500 years ago, the debris that had accumulated (sediments) collapsed again, creating a mudflow. Lava then flowed over the sediments from the mud flow several times. At an elevation of about 550 m, there is a natural spring that flows out from the cliff where the lava flow ends. It is thought that Shishigahana Wetland was created by the large amount of water flowing from this spring.

“Chōkai marimo” that grows in the running water here is a rounded collection of mosses, named for its resemblance to the ball-shaped marimo. The largest Chōkai marimo is over 1 m long. It looks as if the moss is simply growing on rocks, but the mosses themselves actually grow in that rounded shape, without clinging to rocks.