Sanage Onsen Hotel Kinsenkaku

Kinsenkaku sits at the end of a mountain road below Mt. Sanage, about an hour's drive from Nagoya. Its spring is a natural radon water that you can actually drink: there's a tap for it in the changing room, and the kitchen cooks with it too. The shared indoor bath, on the fifth floor, looks out over the mountains, with a sauna (no cold plunge, just a cold shower and a chair). Beyond it are three small private outdoor baths, named Gemini, Sirius, and Altair, that guests can reserve by the room; the reclining Altair tub is built for lying back and looking at the stars on a clear night. Some of the higher-category rooms have their own semi-open-air radon bath built in. A walking trail through the wooded grounds passes a small waterfall and an old roadside shrine.