Keio Takaosan Onsen — photo: Thirteen-fri · CC BY-SA 4.0 · Wikimedia Commons
Onsen in Tokyo: is there real hot spring water inside the city?
Search for an onsen in Tokyo and you get a long list of day spas, bathhouses and hotel baths. Some use hot spring water from under your feet, some bring it in by truck, and some use none at all. The short answer is that Tokyo does have onsen, but almost all of the water inside the city is cool and drawn from deep wells, and the only water that comes out of the ground naturally hot is on islands a ferry ride away. This guide goes through the 13 onsen in Tokyo in our records, in three groups: the city, the western hills, and the islands.
The short answer, in numbers
Our records hold 1,538 onsen across Japan, and 13 of them are in Tokyo. Nine have a recorded source temperature. Seven of those reach 25 °C, the legal line at which water counts as an onsen on temperature alone (cooler water can still qualify through what is dissolved in it). Three reach 42 °C, the point at which a bath can run without a boiler, and all three are on the islands. On the mainland, the hottest record is 39 °C.
So the realistic question is not "is there an onsen in Tokyo" but "what kind do I want". A cool, heated city well can still be a good bath. It is just a different thing from a spring that steams.
Central Tokyo: deep wells and black water
Under the Kanto plain, water is found by drilling, often more than a kilometre down. Four of the onsen in our records are inside the 23 wards.
- Ōtemachi Onsen, 0.8 km from Tokyo Station among the office towers, is recorded at 36.5 °C, pH 7.3, a chloride spring, from a well reported at about 1,500 m. The water is used in a hotel's baths, so in practice you bathe in it as a guest there.
- Ōta Ward's black-water springs in the south of the city are recorded at 18 °C, chloride and bicarbonate. This is the 黒湯 (kuroyu), water the colour of strong tea, and several neighbourhood bathhouses around Kamata use it at ordinary sento prices.
- Itabashi Onsen, in the north-west of the wards, is recorded at 17 to 39 °C, a chloride spring. The 39 °C is the hottest record on the Tokyo mainland.
- Asakusa Kannon Onsen, 4.5 km from Tokyo Station near Sensō-ji, is recorded at 26.3 °C, bicarbonate. It has closed, but it still turns up in older lists, so do not plan an evening around it.
Beyond these, many big day spas in the city advertise 天然温泉 (tennen onsen), natural hot spring water. Some draw it from their own deep well; at least one well-known Shinjuku spa has its water brought in daily from the Izu Peninsula. Both are legitimate. The way to tell which you are getting is the spring analysis board near the changing room; how to read it is in onsen vs sento.
Expect the water in the city to be heated, and often recirculated. That is not a trick: at 18 °C or 36.5 °C there is no other way to run a bath.
Western Tokyo: Takao, Okutama and Hinohara
Tokyo runs a long way west of the city, into forested hills on the edge of Yamanashi. Five of its onsen are out here, all on the mainland and all cool at the source, but in a setting that feels nothing like the city.
Keio Takaosan Onsen, 45.3 km from Tokyo Station, is the easy one. It is a day-bathing building right next to Takaosanguchi Station on the Keio line, at the foot of Mt Takao, and it opened in 2015. The water is recorded at 26.2 °C, pH 9.9, simple and sulfur spring, flowing at 300 L per minute. A pH that high is strongly alkaline, which you feel as a slippery smoothness. It is the natural end to a morning walk up the mountain, and the reason it gets busy on weekend afternoons.
Iwakura Onsen, 46.0 km out in the hills of Ōme, is a small valley of inns, recorded at 20 °C, a sulfur spring. The record gives the bus as about 20 minutes from Hannō Station on the Seibu line.
Tsurunoyu Onsen, 66.1 km away near Lake Okutama, has an unusual story. Its original springs were flooded when the Ogōchi Dam was built, and in 1991 the water was pumped back up from beneath the lake. It is a simple sulfur spring, alkaline, and it is carried by tanker truck to inns around Okutama, so a bath "on Tsurunoyu" may be some kilometres from the source. Okutama Station, at the end of the JR Ōme line, is about 20 minutes away by bus.
Deeper in, in the village of Hinohara, Kazuma Onsen (65.5 km) and Janoyu Onsen (65.0 km) sit at the head of the valley. Both are simple springs with high pH on record: 9.0 at Kazuma and 10.5 at Janoyu, one of the most alkaline readings in Tokyo. They are reached by a long bus ride from Musashi-Itsukaichi Station, and the buses are not frequent, so check the last one back before you set off.
There is also Ōme Ishigami Onsen, a sulfur spring with no temperature on record.
The islands: the only naturally hot water in Tokyo
Tokyo also governs a chain of volcanic islands stretching south into the Pacific. They are where the heat is.
Ōshima Onsen, on Izu Ōshima, 109.6 km from Tokyo Station, is recorded at 49 °C, a chloride spring. The open-air bath by Motomachi port is a three-minute walk from the pier. The jetfoil from Takeshiba Pier in central Tokyo takes at least 1 hour 45 minutes, so this is a realistic overnight trip.
Jinata Onsen, on Shikinejima, 159.7 km away, is recorded at 80 °C and classed as an iron spring. It is a rock pool on the shore where the hot water mixes with the sea, so how hot it is depends on the tide: the higher the tide, the cooler. It is free, and swimsuits are worn. It is about 25 minutes on foot from Nobushi port, and the jetfoil from Takeshiba takes roughly two and a half to three hours.
Hachijō-jima Onsen, on Hachijō-jima much further south, is recorded at 41 to 61 °C, with chloride, bicarbonate, sulfate and iodine springs, and several baths around the island. It is reached by a flight of about an hour from Haneda, or an overnight ferry.
These islands are a real trip, with weather that can cancel boats. But they are the only places in Tokyo where you will see hot water coming out of the ground.
Which one, for the time you have
- An evening in the city: a neighbourhood bathhouse on black water in Ōta Ward, or a city day spa. Check the board for the source, and expect heated water.
- Half a day: Mt Takao and Keio Takaosan Onsen. It is the simplest onsen outing from central Tokyo that does not need a car or an overnight stay.
- A full day: Okutama or Hinohara, for a mountain valley and a bath, if you are happy with infrequent buses.
- A weekend: Izu Ōshima for the island version, or leave Tokyo for a real onsen town. Water at 88 °C in Yugawara, or the mountain springs of Hakone, are under two hours away; the three best onsen towns near Tokyo and onsen from Tokyo compare them.
Things to know before you go
City day spas usually provide towels and soap, and charge for them; neighbourhood bathhouses often do not, so bring a small towel and cash. The island baths by the sea are mixed and taken in swimsuits, which is the exception, not the rule; see onsen and swimsuits.
Tattoo rules vary from one place to the next, and large city spas are often the strictest. See going to an onsen with tattoos, and check with each place.
And the same rules apply in a city spa as in a mountain inn: wash before you get in, keep the towel out of the water, and keep your voice down. Onsen etiquette has the full list.
For a bath without staying the night anywhere, see onsen day trips. If you are flying in or out, onsen near Japan's airports covers Haneda and Narita.