Lava caves at the foot of Mt. Fuji
Aokigahara Jukai Forest which spreads in the Lake Saiko area to the northwest of Mt. Fuji is the only primeval forest in Japan to grow on top of ancient lava. Numerous lava caves were formed from lava flows emanating from Mt. Fuji of which about half exist within the forest. Among these, Narusawa Ice Cave and Fugaku Wind Cave are National Natural Monuments which are popular tourist spots in the Mt. Fuji vicinity. The average temperature in the caves hovers at around 3 degrees Centigrade so that it is refreshingly cool even in summer.
Narusawa Ice Cave with its undulating shaft
Narusawa Ice Cave has a total length of 153m and height ranging between 1 and 3.6 meters. Since the interior forms a loop, you can make your way around the cave. The highlights include icicles created from water drops sprouting from the ceiling. Even during the summer in the middle of a forest at 1000m altitude, the icicles never melt away. They make their longest growth around April, and depending on the year, icicles of 3 meters in height with a diameter of 50cm can be observed. Features such as an ice pond so large that it extends as far as the ground, walls, and ceilings of caves down as far as Enoshima are said to exist.
Fugaku Wind Cave which can be easily navigated even by kids
Located just 5 minutes away by car from Narusawa Ice Cave, Fugaku Wind Cave measures a total length of 201m and a height of 8.7m. Since the temperature has remained stable throughout the year, silkworm eggs were once stored in the cave up to the Meiji Era. The 15-minute observation course is easy to walk for both children and senior citizens during which features such as icicles that never melt in summer, lava shelves, ropy lava, and glowing blue-white moss on the rock walls can be seen. There are also restaurants in the area so that you can sample local dishes such as Fujinomiya yakisoba and Yoshida udon.