This limestone cave, with a total length of approximately 450 meters, is designated as one of the prefecture’s natural monuments. Of particular note is the Ryugubashi (Undersea Palace Bridge) which crosses a subterranean lake in the innermost cavern. Also, there are rimstones within the cave which resemble rice terraces. The cave, engulfed in silence and stillness, is lit up with colorful LED lights, giving a mysterious atmosphere.