Takaragawa Onsen

From Minakami town, the road follows the Tone River upstream for about thirty kilometers, climbing into the mountains of northern Gunma before the valley narrows and the asphalt begins to feel borrowed from somewhere else. There is a final bridge, the river is very loud beneath it, and then you are in the car park of Takaragawa Onsen Osenkaku, surrounded by cedar forest with the sound of water coming from multiple directions at once. The inn sits directly on the Takaragawa, which means the Treasure River, and the outdoor baths are not near the river so much as built into its bank.

The four rotenburo here are enormous. The largest, called Kodokara, can take 200 bathers at once across its 300-plus square meters of open-air pool, built from river boulders stacked into low walls that separate the bathing areas from the actual river channel without blocking the view. Three of the four pools are konyoku, open to all genders, which is uncommon enough in contemporary Japan that it draws visitors specifically for that reason. You step down from a wooden changing area directly into hot water surrounded by real rock, with the Takaragawa running clear and fast just meters away and the forest rising on both sides of the valley.

The water is a sodium-chloride and sulfur type, running 40 to 42 degrees Celsius, clear and without strong odor, with a warmth that settles into your muscles rather than just heating the surface of your skin. The saltiness is barely detectable as a taste if you get any on your lips, but you can feel it as a slight weight on your skin, particularly your hands and forearms, after a long soak. The longer you stay in, the heavier that feeling becomes, and it takes a while to fully rinse off under the showers afterward.

The visual moment that Takaragawa is known for is winter, and specifically the image of the outdoor pools under heavy snowfall. Snow collects on the boulder walls and piles up on the wooden walkways while the water steams in the below-zero air, and the river alongside runs black against the white riverbanks. You can sit in the hot water and watch snow fall into the river downstream. It is a scene that appears in every guide to Japanese onsen, and it earns its reputation. But the less-photographed version of Takaragawa, in late autumn when the maples on the valley walls turn and shed into the river current, is just as striking and significantly less crowded. The boulders hold the fallen leaves in eddies just outside the pool walls, and the water picks up a faint orange cast from the tannins.