Opened in…705 AD and declared oldest hotel in the world, Nishiyama Onsen will take you for a journey through time. In fact, it's been operated by the 52 generations of the same family. Modern conveniences have been added to hotel, so you can enjoy your stay a bit more than all the people who slept here before you throughout the last 1300 years. Local onsens are renowned in Japan, and are using natural hot springs gathering water from the place 888 meters below the ground.
Sleeping here is an outstanding experience - one and only kind. Hotel might be a bit difficult to reach and expensive, but then such great things aren't and shouldn't be any easier.