Many visitors ask how to find onsen (hot springs) in Tokyo.
Onsen is a kind of trade mark, and only baths containing water from a spring can claim this title. Plus, those waters have either to naturally glush or be pumped at more than 25°C, or to contain more than a specific amount of chemical derivatives.
There are many
sento in Tokyo. Those are traditional or modern bathhouses, where people use to go to wash their body, to relax and to socialize. Most of them use however normal tap water, adding sometimes extra ingredients to the bath (most often: aromatic herbs). Sento are not onsen, as they are not using a natural spring.
There are however in Tokyo, or surrounding areas, a small number of real onsen, whose water is usually pumped up from high depth. Here is a list of the most popular ones. Keep in mind that bathing in those Tokyo onsen is a very different experience from visiting an onsen in the countryside. In particular as most of them require visitors to wear a swimming costume.
LaQua
Address – 1-1-1 Kasuga, Bunkyo-ku, Tokyo
Phone – 03-3817-4173
Opening hours – 11 am to 9 am
Price – 2'565 yen (extra added to use the facility after midnight)
Public transportation – Suidobashi station (JR Chuo-Sobu Line & Mita Subway Line) and Korakuen (Nambuko Line)
Internet –
www.tokyo-dome.co.jp/e/laqua/index.htm
In the heart of the new complex in Korakuen, this onsen offers limited interest for onsen lovers, as the number of baths is reduced to the minimum. There are however many other attractions there, including a large number of shops and restaurants, as well as the famous Thunder Dolphin roller coaster.
Oedo Onsen Monogatari
Address – 2-57 Aomi, Koto-ku, Tokyo 135-0064
Phone – 03-5500-1126
Opening hours – 11 am to 9 am (last entry 2 am)
Price – 2'827 yen
Public transportation – Telecom Center Station (Yurikamome Line); Free shuttle bus from Tokyo Teleport Station, Riukai Line
Internet –
www.ooedoonsen.jp (Japanese only)
Designed as a kind of onsen water park with a strong influence of the Edo period, this place provides a nice relaxing escape from the usual Odaiba attractions. Segregated traditional onsen baths and a large mixed foot bath outside, where guests have to wear a yukata (provided).
Zaboo
Address – 東京都港区西麻布1-2-10 〒106-0031
Phone – 03-5770-8100
Opening hours – 10:30 am to 9 am
Price – 2'880 yen
Public transportation – Roppongi Station (Toei Oedo Line & Hibiya Line)
Internet –
www.zaboo.jp (Japanese only)
Close to the heart of Roppongi, this is a nice (and expensive) place to enjoy a natural onsen. Many small inside and outside baths, all segregated, as well as a foot bath next to an open-air cafe. Several sauna and relaxation rooms are also available.
Takaido Natural Spa - Utsukushi no Yu
Address – 東京都杉並区高井戸西2-3-45 〒168-0071
Phone – 03-3334-0008
Opening hours – 10 am to 12 am
Price – 800 yens on week days, 1200 yens on week-ends
Public transportation – Takaido Station (Keio Inogashira Line)
Internet –
www.nafsport.com/utsukushi/index.html (Japanese only)
Small onsen not too far from the center of Tokyo. Inside baths and smaller outside ones, as well as an "onsen pool".
Seta Onsen Sanganoyu
Address – 4-15-30 Seta, Setagaya Ward
Phone – 03-3707-8228
Opening hours – 10 am to 11 pm
Price – 2300 yens (coupon available on the web site for week days)
Public transportation – Futako Tamagawa (Tokyu Denentoshi Line, 10 minutes by foot)
Internet –
www.setaonsen.co.jp/english/index.html
Water pumped from 1'700 meters, and cooled from 46°C. There are traditional Japanese baths, plus an open-air jacuzzi type bath, for which swimming costume have to be worn (rental available). Massage and esthetic services are also available.
Toshimaen Niwanoyu
Address – 3-25-1, Mukoyama, Nerima-ku, Tokyo
Phone – 03-3990-4126
Opening hours – 10 am to 11 pm (last entry 11 pm)
Price – 2250 yens (coupon available on the web site for week days)
Public transportation – Toshimaen (Oedo Line & Seibu Ikebukuro Line)
Internet –
www.toshimaen.co.jp/niwa-yu/niwanoyu.html
An impressive complex with separated men and women areas including inside and outside baths, as well as sauna. Those zones are linked by a large "Bade Zone" where swimsuits are required, consisting of a large pool, a small "Dead Sea" bath, outside smaller round baths and a Finnish sauna. Large relaxation rooms are also available.
Machida Roten Garden
Address – 東京都町田市相原町358番地
Phone – 042-774-2681
Opening hours – 10 am to 12 am
Price – 1000 yens on week days, 1200 yens on week-ends
Public transportation – Futako Tamagawa (Tokyu Denentoshi Line, 12 minutes by foot)
Internet –
www.haragroup.co.jp/roten
The water of this onsen is pumped from a depth of 1'381 meters, and has a natural temperature of 37.2°C. Traditional bathing only, with several outside baths. Different types of saunas are also available.
Hinode Mitsuzawa Tsuru-tsuru Onsen
Address – 4718 Oguno, Hinodemachi, Nishi-Tama-gun, Tokyo
Phone – 042-597-1126
Opening hours – 10 am to 8 pm, closed on Tuesday
Price – 800 yens for up to 3 hours
Public transportation – take the JR Itsukaichi Line to Musashi-Itsukaichi Station, and then the bus to the terminal stop Tsuru-tsuru Onsen
Internet –
www.tourism.metro.tokyo.jp/english/spot/hinode1.html
In the nature, this place is a good spot after a hiking day – there are several interesting trails around. Several inside baths, as well as a rotenburo.
Calendar 
Counter
Front
Coin Laundry
Parking
Massage Machine
Bubble bath
Vibration bath
Bed style bath
Electric bath
over 45 degrees bath
Body massage
Radon, radium bath
Roten buro (outside bath)
Sauna
Cold water bath
Under 40 degrees bath
Black color water bath
Onsen
Vending machine
Karaoke
Open early morning
Soft water
Shower
