The Ryusendo Caves are one of the three biggest caves in Japan, and designated as a National Natural Monument. What has been explored of the cave system is already over 2,500m long, and it is hypothesized that its total length is more than 5,000m. Also, from its depths fresh spring water wells out in several places, creating subterranean lakes. Among them, the Third Subterranean Lake is 98m deep, and the Fourth Subterranean Lake is 120m deep, the deepest in Japan, and boasts some of the clearest water in the world. The pure, unadulterated lake water breathes the wholesomeness of nature and the endless stalactites within the cave lure you into a different, haunting world where the wonders and mystery of nature are revealed.