Akiyoshido Cave Overview
Tucked beneath the Akiyoshidai Plateau in Mine city, Yamaguchi Prefecture, Akiyoshido is one of Japan’s largest and longest limestone caves. Stretching 10.7 kilometers in total length, it ranks as the second longest cave in Japan, after Iwate Prefecture’s Akkado. The roughly 1-kilometer public tour route is illuminated and paved, making it accessible to most visitors.
The cave’s history stretches back around 300–350 million years. Over millennia, coral reefs built up and were covered by sediment, forming layers of limestone that were pushed above the surface by tectonic activity. Rainfall then gradually eroded those layers, carving out the remarkable karst formations and underground chambers that exist today.
In 1926, Crown Prince Hirohito visited and the cave was renamed Akiyoshido in his honor. It has since been designated a Special Natural Monument by the Japanese government.
Along the tour route, highlights include the Hyakumaizara — a cascading series of over 500 rimstone pools resembling terraced rice paddies — as well as the Senjojiki cavern, which is 80 meters wide and 175 meters long, with a ceiling draped in stalactites. An optional adventure path (¥300 extra) leads visitors to a higher vantage point within the cave. The temperature inside stays at a constant 17°C year-round.
Best Times To Visit Akiyoshido Cave
Akiyoshido is open and enjoyable year-round thanks to its stable underground temperature, but the surrounding Akiyoshidai Plateau changes dramatically with the seasons. Spring and summer bring fresh green landscapes, autumn turns the plateau reddish yellow and winter dusts it with snow.
One of the most spectacular seasonal events takes place in February, when the mountainside is set alight to control plant growth over a period of three hours with the help of around 1,000 local volunteers. This annual controlled burn is a striking tradition that draws visitors from across the region.