Takegawara Onsen is one of those quintessentially Japanese experiences - they literally bury you in volcanic-heated sand while you're wearing a yukata! The historic building itself, dating back to 1879, looks like something straight out of a period drama with that distinctive wooden roof.
The whole concept sounds both bizarre and amazing - you get covered in naturally heated sand under this beautiful historic wooden building. While we didn't make it there ourselves, it's definitely on our "next time in Beppu" list because, honestly, how often do you get the chance to be therapeutically buried in hot sand?