Zaō Onsen — photo: 663highland · CC BY-SA 4.0 · Wikimedia Commons
Zao onsen: the acid water, the big outdoor bath, and getting there
Zao is known abroad for skiing and for the "snow monsters", the frozen trees near the top of the ropeway. It is also an old bath town on water that is rare in Japan, and rarer still in this part of it. Most guides give you the ski runs, the ropeway and a photo of the big outdoor bath. This one is about what they leave out: what the water is and what it does to you and your belongings, why the famous bath is shut for most of the ski season, how the town differs from the onsen on the Miyagi side of the same mountain, and how it compares with Nozawa if the bath is part of why you are going.
What the numbers say
Our records list five water types at Zao: acidic, sulfur, chloride, sulfate and iron. Of the 1,468 towns in our database with a water type on record, 29 list five or more. Many of those are districts of Hakone, Nasu and Beppu counted separately; as distinct places there are about a dozen, and Zao is one of them.
The acid is what matters. Only 47 towns in the database list acidic water, and 32 list it together with sulfur. Zao has exactly the same five types as Sukayu in Aomori, Sukawa in Iwate and Beppu in Kyushu. Closer to home it stands alone. There is no other acidic town within 48 km of Zao; the next is Ubayu, a single inn in the mountains near Yonezawa. Yamagata has two acidic towns in all, and Miyagi, next door, has none. For anyone based in Sendai or Yamagata, Zao is the only strong acidic water within easy reach.
We do not have a source temperature or pH on record for Zao, so we do not quote one here. What you will notice is the smell of sulfur through the whole town, water that is pale and cloudy rather than clear, and a sharp, slightly sour feel on the skin. For how acidic water compares with other types, see reading the water sign.
What acidic water does
This is the part the ski guides skip, and it is the part that affects your stay.
- It stings. Any small cut, graze, chapped lip or shaving rash will sting as soon as you get in. It usually settles after a minute; if it does not, get out.
- Keep it away from your eyes. Do not splash your face or put the small towel over your head after dipping it in the bath. If water gets in your eyes, rinse with tap water.
- Take off jewellery. Silver turns black, and other metals can discolour. Leave watches, rings and chains in your room. Old coins, keys and glasses frames suffer too.
- Rinse off afterwards with tap water if your skin feels dry or itchy.
- Short soaks. A few minutes at a time, with breaks, is how most people use strong water. Drink water before and after, and do not bathe after alcohol.
Towels and white clothing can pick up a faint yellow tint and the smell of sulfur. Use the towels your inn gives you rather than your own.
The big outdoor bath, and when it is closed
The picture on most Zao pages is the 大露天風呂 (dai-rotenburo), a set of large rock pools beside a mountain stream in the woods above the town, with separate sides for men and women. It is a day-use bath with an entrance fee, a short uphill walk from the top of the town.
It is closed in winter. The season usually runs from spring to late autumn, and the bath shuts before the snow; the exact dates change each year. That means the bath in the photos is not open during most of the ski season, when most foreign visitors come. If it is the reason you are going, go between late spring and autumn, and check the dates first.
In winter, bathing happens in your inn and in the town's small public baths, the 共同浴場 (kyōdō yokujō). There are three in the centre, each a single room with a tub, used by locals every day. They cost little or nothing; read the sign at the door. They have no soap, no towels and often no shower, so bring a small towel, wash with water from the bath, and leave the space as you found it. A few larger day-use baths in the town stay open all year. The general rules in our etiquette guide apply, and the acid adds one more: do not drip bath water on the changing room floor, which it stains.
The snow monsters, and the crater lake
The 樹氷 (juhyō) are fir trees near the summit coated in ice and snow by the winter wind, until they look like figures. They are reached by the ropeway from the town and are at their best in the coldest weeks, roughly January and February, with evening light-ups on some days. Dress for the top of a mountain, not for the town.
The other famous sight, the 御釜 (Okama) crater lake, is on the summit ridge between Yamagata and Miyagi. It is reached by the mountain road across the range, which is closed in winter and usually opens in spring. You cannot bathe there. It is a lookout, not a spring.
The other side of the mountain
Zao is the name of a whole mountain range, and "Zao onsen" in searches sometimes means the Miyagi side, known as Miyagi Zao. The water there is nothing like Zao's.
Tōgatta, 16 km from Zao in a straight line, is recorded at 70 °C with chloride and sulfate water. Gaga, a single inn 9 km away, is at 58.1 °C with bicarbonate and sulfate water, pH 6.6. Aone is at 43 °C with six inns. None of them is acidic. They are closer to Sendai by bus, and in summer the road over the crater links the two sides. In winter it does not, and moving between them means going round by Sendai or Yamagata.
If you want acidic water, stay in Zao. If you want a quieter, gentler bath and you are coming from Sendai, the Miyagi side is easier.
Getting there
Zao is 11 km from Yamagata Station, 43 km from Sendai Station and 282 km from Tokyo Station, in a straight line.
- From Tokyo. The Yamagata Shinkansen runs to Yamagata Station in roughly two and a half to three hours. From the bus stop at the station, buses to the Zao bus terminal take about 40 minutes. If you plan to use a rail pass, check that it covers the Yamagata Shinkansen before you buy it.
- From Sendai. Highway buses and the JR Senzan Line both reach Yamagata in about an hour and a bit, then take the Zao bus. In the ski season there are sometimes direct buses from Sendai; check the current timetable.
- From Kyoto or Osaka. Shinkansen to Tokyo and on to Yamagata, most of a day, or fly to Yamagata or Sendai.
The town is on a steep slope, and in winter the lanes are packed snow. Many inns will collect you from the bus terminal if you tell them your arrival time. A day trip from Sendai or Yamagata is easy; from Tokyo it is long. One or two nights is usual, more if you are skiing.
Zao and Ginzan
Ginzan, the old silver-mining street with the lamps and the wooden inns, is 46 km away, and many people try to fit both into one trip. They are on different branches from Yamagata: Ginzan is reached from Ōishida, further up the Yamagata Shinkansen, then by bus. Allow half a day to move between them. Ginzan's water is salt and sulfur, recorded at 44 to 65 °C, and not acidic. For more on Ginzan and the rest of the region, see our Tohoku onsen guide.
When to go
December to March is the ski season, the snow monster season and the busiest, most expensive time. The big outdoor bath is closed. The town is full of skiers, and the small public baths are crowded in the evening.
From late spring to autumn Zao is a quieter hot spring town. The outdoor bath is open, the road to the crater is open, and there is walking on the mountain. Autumn colour comes to the mountain earlier than to the town. See when to go for more.
Zao or Nozawa?
These two come up together because both are ski towns with a strong bathing tradition. For the snow, look elsewhere. For the bath, they differ in three ways.
The water. Nozawa is sulfur water recorded at 42 to 90 °C: very hot, mild on the skin, mostly clear. Zao is acidic sulfur water that is cloudy and stings cuts. If you want strong water, Zao; if you want very hot water that is easy on the skin, Nozawa.
The public baths. Nozawa has thirteen free village baths within walking distance of each other. Zao has three small ones in the town, and its big outdoor bath is closed in winter.
Getting there. Nozawa is about two and a half to three hours from Tokyo; Zao is a little longer, but close to Sendai. For a trip based in Tohoku, Zao; from Tokyo or the Japanese Alps, Nozawa. For the other strong acidic town near Tokyo, see our Kusatsu guide.
Things not to do
Do not wear silver or other jewellery into the water.
Do not put your face in the bath or rub your eyes with a wet hand.
Do not go to Zao in January expecting the big outdoor bath to be open.
Do not mix up Zao with Miyagi Zao when booking; they are on opposite sides of the mountain, and in winter far apart by road.
Do not assume tattoos are fine. Policies vary by bath and by inn. See going to an onsen with tattoos, or book an inn with a private bath.
New to this? Start with how an onsen stay actually works and onsen etiquette. For the water, see reading the water sign and our sulfur onsen guide. For the region, see Tohoku onsen.