With a pH level of 1.2 Tamagawa Onsen is regarded as the most acidic onsen in Japan -- and possibly the world. This hot spring is located in the Akita Prefecture part of Towada-Hachimantai National Park. It's close to Mt Hachimantai and the popular Hachimantai Aspite Line scenic route. However, accessibility is limited in winter due to heavy snowfall. What\u2019s Tamagawa Onsen known for? The acidic waters of Tamagawa Onsen are thought to have particularly strong healing properties. In fact, many people travel there specifically for that reason -- particularly the elderly and sick. To be honest that lends the place a serious feeling, so it's not an ideal destination for those after a light-hearted hot spring vacation. That being said, if you want to try the most acidic onsen in Japan, you've probably got some gumption. Be warned though, the water really is acidic -- if you stay in for too long you may suffer acid burns. To help visitors bathe safely, there are plenty of signs around with advice on how to use the baths, but they're mostly in Japanese. However, the general gist is: Don't stay in the water for more than 5 minutes at a time Don't submerge past your shoulders (avoid getting the water on your neck and face) Get out if you feel pain or discomfort -- don't try to power through Shower thoroughly after using the baths And even if you do follow all these guidelines, you'll probably come out a little pink and tingly. Also, you'll smell. In addition to its acidicity (or maybe because of it), Tamagama Onsen has a very strong sulphric smell. It will stick to your body, clothes and towel -- trust us, we know from experience. What kind of baths are there? We'll say this, Tamagawa Onsen is not a one-trick-pony -- in both the men's and women's sections there are multiple baths to try. The standard pools range in both acidity levels and temperature. This is indicated by signs in Japanese near each bath, but the key things to look for are '50%' and '100%' which indicate the level of acidity. It's recommended that you start with a 50% bath. Temperatures range from 40 to 50 degrees celsius. Don't overlook the more unique baths. In the \u5bdd\u6e6f (neyu, bed bath) you recline in a shallow pool, complete with a wooden 'pillow' to rest your head on. While in the \u6253\u305f\u305b\u6e6f (utaseyu, waterfall bath) you sit on a bench under a 'waterfall'. Finally, the \u7acb\u6e6f (tachiyu, standing bath) is deep enough for you to stand in and be submerged up to your shoulders. There's also a sauna and a steam box (a wooden box that you sit in with your head sticking out of the top) that both use steam from the acidic waters. Oh, and if you really want to go all out there's a drink area where -- in addition to cool fresh water -- there is a tap for the acidic water that you can drink. But don't drink the acidic water straight, make sure to dillute it with the fresh water. Signs -- in Japanese -- explain exactly how to do this, but they have photos that are easy enough to follow. Aim for a ratio of 1 part acidic water to 5-8 parts fresh water. Drink it slowly, and make sure to rinse your mouth out after to protect your teeth. Outside of the main bath area, you'll also find an outdoor foot bath and an indoor bed rock bath. There are also two private baths with 50% acidity but these are for overnight guests only. Visiting Tamagawa Onsen The entrance for day visitors is different to the one for overnight guests, but a member of staff will point you in the right direction. You buy entry tickets from a vending machine just inside the entrance for . Rental towels are also available for an extra -- and we actually recommend getting one because the smell can be hard to wash out. There are free shoe lockers near the entrance as well as coin lockers for valuables. Day visitors can use the baths from 9 a.m. to 4 p.m, but last entry is at 3:30 p.m. Note: Due to the acidity of the water visitors are advised to remove all jewelery and other metal or electronic items (smart watches for example) before entering the baths. Are tattoos allowed? There are no signs at Tamagawa Onsen that prohibit tattoos. Similarly, there is no information on the official website saying if tattoos are\/are not allowed. This author has several small\/meduim tattoos and was not asked to cover them by staff members, but your mileage may vary. Can you stay there? Yes, part of the Tamagawa Onsen building is set up as a ryokan (Japanese style inn). There are both Japanese and Western-style rooms, and both room types have TVs, fridges and toilets. Two meals per day are included in the room price, however there is a 'room only' option. Guests who opt for 'room only' can make use of the shared kitchen, or pay separately for meals. Keep in mind that staying here is intended to be a longer term theraputic experience. What other facilities are there? There is a restaurant near the front of the building, but due to the very early 1 p.m. last order we can't comment on the taste or price of the meals. However, there is also a food stall that sells local Akita Prefecture specialities and soft serve icecream that's open until 3:30 p.m. The souvenir shop sells a similar range of local food products, and special Tamagawa Onsen products like bath salts. Near the main bathing facilities there are vending machines that sell alcohol and local produced milk, as well as standard fare like tea and sports drinks. There is also a small rest area here, as well as others throughout the building. Other facilities include a shared kitchen (for overnight guests), coin laundries and a massage room. What amenities are in the baths and change rooms? The change rooms are fairly small, but there are some lockers and basic amenities like hair dryers. Similarly, the baths have bottles of body wash, shampoo and conditioner, but nothing too luxurious. What\u2019s nearby? Right next to Tamagawa Onsen you'll find the Tamagawa Shizen Kenkyu Road (link in Japanese), a nature trail that will take you to the source of the hot springs. The nearby Mt. Hachimantai and Mt Iwate are hard to miss. If you travel to the area outside of winter, you can enjoy a scenic drive along the Hachimantai Aspite Line. How do you get there? The most important thing to know about getting to Tamagawa Onsen is that in winter, most of the roads are closed to general traffic. Outside of winter, you can easily drive from Morioka City (actually over the border in Iwate Prefecture) in a little under 2 hours. There is free parking just a short walk from the main building. The other option is to take a bus. Direct buses depart from either Tazawako Station or Kazunohanawa Station, and take 60 to 90 minutes. It will cost you a little under one-way, with 1 to 2 departures per hour. In winter buses only operate from Tazawako Station.