When you think of an onsen, what springs to mind? Tranquil steaming pools surrounded by misty mountains and bamboo groves? This is probably the the ideal image of a hot springs getaway, but there are actually over 200 onsen facilities to be found amidst the high-rise office blocks and busy roads of central Tokyo. And there’s soon to be one more to enjoy in Otemachi, right in the heart of Tokyo’s business district.

A bit about onsen

‘Onsen’ is the Japanese word for hot springs, used to describe both the spring itself as well as the facilities found around them. Hot springs are geothermally heated groundwater that either emerges from the ground naturally or can be drilled down to and pumped up to the surface. This heated water is often high in mineral content, which has led to the belief that bathing in an onsen can be beneficial for certain aspects of health depending on the mineral composition of the water.

Onsen in Tokyo

According to a member of the survey agency who analyzed this latest onsen, if you dig down between 1,000 and 2,000 metres anywhere in Tokyo, you’re likely to hit upon an onsen. Since 1980 onsen development within Tokyo has increased due to comparatively lower costs of mining, and the ability to dig down further and further. In Takaban, Meguro Ward, there is an onsen facility that draws water from just 90 metres underground, but recently there are more and more that draw their water from over 1,000 metres below the surface.

As of March 2013, there were 257 onsen facilities within the Tokyo Metropolitan Area, with 114 of those located within the 23 wards. However, the actual hot springs themselves are found at only 81 spots, so there are many places where facilities share the same onsen source, sometimes with up to five facilities competing against each other.

▼ It doesn’t look like much yet, but come 2020 a huge business and leisure complex will have been built up around the newly found onsen.


Otemachi Onsen

Real estate giant Mitsubishi Jisho has announced that they have mined down to an onsen in the very centre of Tokyo’s business district in Chiyoda Ward, near to Tokyo Station. Between the skyscrapers towering over the Otemachi area, they have drilled down 1,500 metres to get to the source of a natural hot spring. Analysis of the water has revealed that it has a temperature of 36 degrees and contains sodium and iodine, a composition that means it should be beneficial for joint and nerve pain. Michiaki Kamae, director of Mitsubish Jisho’s Marunouchi Development Department, expressed his relief that they actually hit the onsen – it sure would have been a bummer if they’d drilled all that way down for nothing! As it is the first hot spring source to be found in Otemachi, the name  ‘Otemachi Onsen’ was still up for grabs, and that’s what they’ve gone with.

▼ Testing the waters.


Planned Facilities

An 11,200 square metre area in Otemachi is currently undergoing redevelopment, expected to be completed around springtime two years from now. There are plans for a 31-floor office block and an 18-floor hotel, which will also contain a fitness centre. The onsen will attract salarymen and women from the surrounding offices, guests at the Japanese-style ryokan in the hotel tower, and of course the waves of foreign tourists expected with the Tokyo Olympics. In less interesting but no less important plans, they also intend to open the onsen facilities to people and volunteers engaged in rescue activities in the case of earthquake or other disasters.

Providing everything goes according to schedule, come 2020 this could be the perfect place for visitors to take some time to relax between adrenaline-filled Olympic events and sightseeing in the busy capital.

▼ A model of the planned facilities.


▼ News report on the new onsen [Japanese]

Source: NHK, ANN
Header Image: KONA BESSO Spa