Jinata Onsen on Shikinejima Island, Niijima-mura, is an open-air bath with very unusual terrain, as if the earth was split with a knife. The spring water contains iron sulfide, which is said to have positive effects on nerve pain, rheumatism, and sensitivity to cold. The source of the water is about 80 degrees Celsius, so make sure to mix it with sea water and find a temperature that is just right. There isn't much outside light, so visitors at night can spend some blissful time soaking in the onsen underneath a sky full of stars.
*There are no showers at this onsen. Please wear a swimsuit when bathing.

Photograph provided by Tokyo Convention＆Visitors Bureau