Yamagata · Zao Onsen
Zao Onsen Dai-Rotenburo
蔵王温泉大露天風呂
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.
- Price (adult)
- ¥850
- Hours
- Weekdays 09:30–17:00 (last entry 16:30); weekends & holidays 09:30–18:00 (last entry 17:30)
- Closed
- Closed in winter (late Nov–late Apr); occasional maintenance days
- Access
- 20 min walk from Zao Onsen bus terminal
- Water type
- Acidic spring
- Tattoos
- Ask ahead
- Admission
- Adults ¥850 / children (1–11) ¥400 per the official price list; some tourism sites show ¥1,000, so confirm on site. Coin lockers ¥100, towels sold. Night “starry rotenburo” sessions (selected dates Jun–early Oct, 18:30–21:00) ¥1,000 / ¥500, no discounts. A combined day-bath ticket for four facilities launched July 2026
- Baths
- At the far end of the resort, huge gender-separated open-air pools of natural stone stepped in two tiers along the Sugawa gorge (each holds ~100). Nail-free timber changing building. Free-flowing, so no showers or washing area; no soap or shampoo
- Water
- Acidic sulfur-aluminium sulfate-chloride spring, 50.8 °C at source, strongly acidic at pH 1.9, ~735 L/min. Milky to bluish white. Nicknamed the “beauty-making bath” and “soap-free bath”. Not drinkable
- Parking
- Free dedicated parking for 60. Enter 023-694-9718 (Terrace Sunpal) in your sat-nav to reach the car park. The access road is very narrow
- Phone
- 023-694-9417
- Official site
- jupeer-zao.com ↗
- Open in Google Maps
- Google Maps ↗
Essentials
Stay in this onsen town
Compare and book stays in Zao Onsen. Day bathing itself needs no booking.
Opens partner booking site (affiliate)
Why go
- Terraced tubs jutting into the gorge
- Extremely acidic sulfur water (pH ~1)
- Summer-only night-time bathing
A milky, strongly acidic rotenburo for 200 along the gorge
The Zao Dai-rotenburo lies at the very top of the resort, up the Sugawa gorge: stepped natural-stone pools holding around 100 bathers per gender, the emblem of Zao’s green season. The source, one of Japan’s most acidic sulfur springs at pH 1.9, gushes 735 litres a minute straight into the pools, milky shading to blue, while the stream, birdsong and cool highland air wash over you. Pass through the nail-free timber changing hall, descend the steps and the forest and river open out in front of you. It operates only from late April to late November (2026 opening: 25 April), with lantern-lit “starry rotenburo” nights on selected summer and autumn dates.
Tips & cautions
- Seven official rules for the strongly acidic water: always rinse first / don’t scrub / it hurts badly in the eyes / not drinkable / remove all jewellery (metal corrodes black) / dry off well as it damages clothing / floors are slippery.
- No showers or washing area, no soap — soak only; wash at your inn first.
- Feels hot; the upper tier is hotter, the lower gentler.
- Closed late Nov–late Apr and on snow/maintenance days (2026: 4 Jun and 13 Jul).
- ~20 min uphill walk from the village (1.1 km from the ropeway bus stop); icy mornings possible.
- Open till 18:00 at weekends; dusk is the most beautiful time.
Getting there
Yamako bus ~40 min from JR Yamagata Station to the Zao Onsen terminus, then 18–20 min uphill on foot, or 1.1 km from the “Chuo Ropeway-mae” stop (Arashiki 853-3). By car ~20 km / 35 min from Yamagata-Zao IC via Routes 13 and 21. Free parking for 60. ~1 h 40 min by highway bus from Sendai.
Before you go
- No official tattoo policy is published — ask at reception.
- Strongly acidic water — rinse off afterwards, avoid long soaks, and remove silver jewellery.
- Open seasonally only — check the official site for operating dates before you go.
- Last entry is 30–60 minutes before closing.
Features
Mood & scenery
Convenience
Price
Amenities
✔ Verified operating: 2026-09 Operating status and rates cross-checked against the official site and onsen guides (full source notes in Japanese on the JA page)
Prices and hours change. Check official sources before visiting.
More in this area
Shirogane-yu (Ginzan communal bath)
A Kengo Kuma-designed communal bath at the entrance to Ginzan's Taishō-era street. Hot water with drifting mineral flakes for ¥500. The one place day visitors can bathe in Ginzan's water — reception closes at 3:30 pm.
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.
Ginzan Onsen Ginzansō (Day Bath)
The large ryokan at the entrance to Ginzan. Indoor, open-air and lie-down outdoor baths — far roomier than Shirogane-yu. Day use 11:30 am–2 pm (last 1:30), ¥1,500, closed Thursdays; day bathing has been suspended and resumed repeatedly, so check the website. Cash only.
