Minakami, Gunma, Japan
Japan's largest open-air onsen
Info updated: 2026-03
Details may differ from actual conditions.
Est. 1923. Japan's largest mixed outdoor onsen, 4 baths (470 tatami). Thermae Romae II location.
Baths
5120 tatami, mixed, built 1940
200 tatami, mixed, largest
50 tatami, mixed
100 tatami, women only
Facility details are verified and updated regularly, but may differ from actual conditions. Please confirm with the venue before visiting.
Japan's largest mixed-gender outdoor onsen with 4 giant baths totaling 470 mats
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