Living in one of the most volcanically active countries in the world can have its perks, not least the abundance of natural hot springs. According to the Nippon Onsen Research Association, there are a total of 3,185 onsen spread around Japan, in locations ranging from Hokkaido to the southernmost islands of Okinawa. Traditionally, the citizens of Edo had to trek to spa towns like Hakone and Atami if they wanted to get their fix, but today's Tokyoites have it easier: they just drill a few kilometres underground to tap their own source of geothermal goodness. You can now find a diverse range of onsen in Tokyo, from old-school public baths that are practically indistinguishable from your average sento, to massive, theme park-style complexes such as Oedo Onsen Monogatari. As winter holds the capital in its rimy grasp, there's never been a better time to check out some of Tokyo's best hot-spring baths – and we've got something for every taste and budget right here...