Nyuto Onsen, one of Japan’s most atmospheric mountain hot spring spots, is also one of the few where men and women can still bathe together. It’s a very romantic far-flung getaway, if one doesn’t mind the other bathers who tend to be shrouded in the steam coming off the baths anyway. Tsurunoyu traditional inn has been serving homely meals over 'irori' hearths with local mountain ingredients for hundreds of years, and welcomes the occasional adventurous westerner. It's what the Japanese call a 'time slipu', where oil lamps are still used in the rooms and the recommended rooms have thatched roofs. It is definitely one for those who seek a fully immersive cultural experience (as well as fully immersive baths!) and don't mind compromising on modern creature comforts for a night or two. Despite its remote location, it is still less than four hours door to door from Tokyo thanks to the bullet train which stops at nearby Tazawako.