The Akiyoshi-dai Plateau is the largest limestone plateau in Japan and has been designated as a special natural monument. The limestone on the plateau was formed during the Paleozoic age as a coral reef in the ocean. Since then, rainwater has dissolved its surface into interesting shapes. The topography you now see is called karst with a typical Japanese style.

The special natural monument Akiyoshi-do cave has a long history which spans 300,000 years. Because of its size and the number and variety of speleothems within, the cave is considered the most important special natural monument in Japan.