|Pseudonym reading||How are you going and how are you going?|
|Specified type||Prefecture designation|
|Type||Natural monuments and geological minerals|
|Designated date||March 8, 1966|
|location||Kuji City Yamagata Town Oji Small Country|
Inner caves are located on the northern hillside of Mt. Toshima (1,263 metres), 500 meters from the inner bay district.
The whole cavern was revealed by the survey in August 1955, and the total length of the combined main and caverns was a large scale of about 1.6km, and it was well preserved in the cave, making it one of the largest caves in Japan.
The dong is divided into the north dong, the south dong, and the lightning dong, and stalactites, stalagmites, and flowstones (limestones covering the wall of the cave) are well developed and magnificent.
In addition, there are paradoxes such as slate that is difficult to dissolve in water and irregular limestone protruding irregularly, and it has high academic value as an example showing the dissolution action of limestone.
In the dong, in addition to bats, primitive insects such as the beetles and nagacomushi are inhabited, and the food chain phenomenon is seen.
The cave is extremely well preserved, and the habitats of these groups of animals in the cave are well maintained.