Yukagen-no-ana

"This sightseeing destination is located on the way to Jinata Onsen, a natural hot spring bath hidden amidst rocky mountains, traveling from the urban center on the east side of Shikinejima Island. Specifically, it is a hole in a stone wall marked with stones inscribed with characters stating in Japanese ""Yukagen no Ana (the hole of bath temperature)"" As its name hints at, the hole is connected to an underground hot spring, and if you stick your hand inside you will be able to feel the warmth it emits. In the winter, the hole even emits steam, and it is a fun destination to visit while checking out the island's natural hot spring baths."