Nagomi no Yu

There aren't many Tokyo spa complexes with a location as convenient as Nagomi no Yu's, just outside the west exit of Ogikubo Station on the Marunouchi and Chuo lines. The outdoor rotenburo baths here are filled with onsen hot-spring water, and complemented by a range of other tubs – including one using carbonated water – and saunas. If you want to go all-out with the pampering, it's worth paying an extra ¥450 to get access to Nagomi's various stone saunas and 'healing' zones, on the third and fifth floors. The complex stays open until 9am each day, and you may even be able to get a good night's sleep in one of the cushioned chairs in the rest areas, though note that there's a ¥1,380 surcharge for people who stay past 1am.