Zao Onsen

Zao Onsen Dai-Rotenburo

A terraced open-air bath along a mountain stream that holds 200 people, with bluish-white strongly acidic sulfur water. Open late April to late November only; closed in winter. Summer starlight sessions at night.

Zao Onsen Kamiyu Public Bath

A log-cabin-style communal bath at the top of Takayu-dōri. Zao's three public baths (Kamiyu, Shimoyu, Kawarayu) all cost ¥200, paid into an honesty box. No washing stations — just rinse and sink into the strongly acidic milky sulfur water.