Akiyoshido Cave

One of the most famous limestone caves in the East, Akiyoshidai Cave is located 100 to 200 meters below the ground at the foot of Akiyoshidai Mountain.
Of the total length of 10,300 meters, approximately 1 km is open to the public as a tourist route.
It is the largest limestone cave in Japan. An underground river flows down for about 1 km from Kotogafuchi at the back of the cave to the cave mouth.

The cave mouth is 24 meters high and 8 meters wide.
The widest part of the cave, “SENJOJIBIKI,” is 80 meters wide and 175 meters long, with a height difference of 35 meters, creating a huge cave space.

The temperature inside the cave is strongly affected by the outside air due to the large cave mouth, with temperatures ranging from 5°C to 18°C near the cave mouth and 16°C at the back of the cave throughout the four seasons.

A 90-meter-deep vertical hole called a kaze-no-ana (windhole) extends into the ceiling at the back of the cave, and the chimney effect creates a column of white water vapor that is warmer than the outside air in winter and blows up into the air. In summer, on the contrary, the air inside the cave, which is colder than the outside air, flows out of the cave mouth and sucks in outside air through the windhole. The chimney effect is also caused by the vertical shaft of the elevator and the artificial tunnel at the entrance/exit of the Kurodani Branch Cave, so measures are taken to prevent this effect.

In summer, the cold air flowing out from the back of the cave in the lower layer and the warm air flowing in from the cave mouth in the upper layer create a discontinuous layer in the cave near the cave mouth, often producing thick fog inside the cave.

Famous Sites
Naga-yuchi: A straight underground river about 15m wide and 100m long. There is a rock shelf at about 10m above the river that shows the remains of the river tens of thousands of years ago.
Hyakkaidara: A limestone flower terrace consisting of a group of stone pools known around the world.
Dongnae Fuji: A huge stone pillar with a diameter of about 5m. The lower part of the column is covered with flowstone, creating a slope like Mt.

Nagafuchi area
Senjyobashiki: 80m wide, 175m long, and with a height difference of 35m, it is the second largest cave in Japan (and the largest existing). The tourist path climbs over a large fallen layer that was created tens of thousands of years ago.
Umbrellas: Many stalactites hang from the ceiling like umbrellas, just like an old umbrella shop.
Daikoku-bashira: Stalactites and stalagmites are connected to form a stone pillar that seems to support the ceiling.
Koganebashira (Golden Pillar): A huge pillar-like flowstone about 15 meters high. It is the symbol of Akiyoshido. In the old days, it was called “Golden Fishing Pillar” or “Golden Pillar.
May Rain Palace: A large space with countless stalactites hanging from the ceiling.