Akiyoshidō

Overview

Akiyoshidō is a limestone cave lying 100–200 m beneath the eastern part of the Akiyoshidai plateau in Mine, Yamaguchi Prefecture, with about 1 km of the cave open to visitors along a walking route. It is regarded as the largest limestone cave in Japan, and an underground river flows down for roughly 1 km from Kotogafuchi deep inside the cave toward the entrance. Designated a Natural Monument in 1922 and a Special Natural Monument in 1952, it lies within Akiyoshidai Quasi-National Park.

Highlights

• ●Japan's largest limestone cave, set 100–200 m below the Akiyoshidai plateau
• ●An underground river running about 1 km from Kotogafuchi to the cave mouth
• ●Designated a Special Natural Monument and listed among Japan's Top 100 Geological Sites
• ●A cave system whose surveyed total length reaches 10,300 m

History

The cave was designated a Natural Monument of Japan in March 1922 and elevated to Special Natural Monument in March 1952. Diving surveys conducted by cave explorers around 1990 from Kotogafuchi confirmed a connection to Kuzugaana, about 2.5 km to the east, giving a total length of 8,850 m. A survey begun in July 2016 by an academic investigation team extended the recorded total length to 10,300 m, currently ranking it third longest in Japan.

Map

34.2281, 131.3035 · Wikidata

Suggested itinerary

1. 1Enter the roughly 1 km walking route open from the cave mouth
2. 2Proceed alongside the underground river while observing the cave formations
3. 3Reach the area near Kotogafuchi deep inside and turn back
4. 4After leaving, tour the surrounding Akiyoshidai Quasi-National Park area

Did you know?

💡 An underground river flows for about 1 km from Kotogafuchi in the cave's depths down to the entrance.

Nearby spots