Get ready for a truly unique experience in Japan! Located on the Oto River, just off the
side of the road, grab a shovel and dig your own onsen! The river still runs cold water but the
pure hot spring water under the ground can get to 72°C. The further down you dig, the hotter it gets so dig it closer to the cool river water to regulate the temperature of your "bath".
From December to February in winter, make sure to check out the Sennin-Buro which literally translates to “1000 people bath” - basically just a very large, man made outdoor onsen. You're still free to dig-your-own onsen if you don't mind standing in the cold for a bit.
Public transportation to Kawayu Onsen is fairly frequent but it might take you a little longer than expected.