Actually wanted to dig 800 meters long !!

The Cave Kannon is located in the Iwanodani Hills (Kannonyama Hills) in the southern part of Takasaki City.

Geologically, it is the “Upper Formation of the Itahana Formation of the Miocene Series of the Neogene Period” more than 5 million years ago. It is a strong layer of rock, mainly composed of gravel, with sandstone and mudstone layers. These layers are thought to be delta deposits that were deposited as the ocean regressed. (Kubo and Tsunoda 1973)

This cave is currently about 450 meters long, including the restricted area, but the original goal was to dig twice as long, 800 meters. Tokuzou chose this location because he thought the strong layers would make it safe for use as a structure, but the excavation work was extremely difficult, as the ground was so hard that the tip of the pickaxe was rounded off and unusable every day. And when Founder Tokuzo died, the work stopped at this point, halfway to the goal. Even today, you can see the excavation process from the top down exactly as it was at the time.