Zao Onsen Dai-Rotenburo
蔵王温泉大露天風呂38°10′ N 140°24′ EDay use¥850, about CAD 7.60 or USD 5.40 (October 2026 rates)Seasonal
The Dai-Rotenburo suits anyone in Zao between late April and late November who wants a big wild bath by a mountain stream; it closes for the whole ski season, so winter visitors use the village's public baths instead.
Know before you bathe
Zao's water is among the most acidic in Japan, so the operator asks for a few things. Pour water over yourself before you get in, scrub gently and keep it out of your eyes. Take off rings and necklaces, because the acid turns metal black. Dry off well afterwards since the water damages clothes, and watch your step on the slippery stone edges.
Getting there
The bath sits above the onsen village beside the stream. You walk through a wooden gate and down a flight of steps to the pools. A car park holds 60 cars.
The Dai-Rotenburo is a set of stone-lined outdoor pools along a stream at the top end of Zao Onsen. You pass the counter and changing rooms in a timber building that the operator says went up without nails, then walk out to the water. The pools are fed straight from the source at 50.8°C. The water is strongly acidic sulphur water at pH 1.9.
On selected Saturdays from June to early October the bath reopens after dark for a starry-sky session from 18:30 to 21:00. Guests carry lanterns down to the water. The 2026 sessions ran on 6 June and finished on 11 October.
There are no showers here, and you can't use soap. Bring nothing more than a small towel, or buy one at the counter. Take your rings and earrings off before you go in, because the acid turns metal black.
Worth knowing
- The village's foliage peaks in early October, and the bath stays open until 17:00 on weekdays and 18:00 at weekends.
- If you're in Zao in winter, head to Kamiyu, Shimoyu or Kawarayu in the village instead. They open all year from 6:00 to 22:00.
Quick answers about Zao Onsen Dai-Rotenburoよくある質問
Is the Zao Onsen Dai-Rotenburo open in winter?
No. The Dai-Rotenburo closes from late November until mid-April each year. In 2026 it opened on 25 April.
How much is the Zao Onsen Dai-Rotenburo?
Day entry costs ¥850 for adults and ¥400 for children aged 1 to 11 in the 2026 season.
Can I use soap at the Zao Onsen Dai-Rotenburo?
No. The bath has no showers and doesn't allow soap or shampoo, because the water flows straight from the source.
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