Japan
Dig your own hot spring in the riverbed — water bubbles up wherever you scrape.
Bring a shovel. At Kawayu Onsen, the Ōtō River runs over geothermal springs so close to the surface that you can dig a hole in the gravel riverbed and watch it fill with hot water. Mix river current and spring heat until the temperature is right, then lie back in your handmade bath while the Kumano forest watches from both banks.
Kawayu Onsen sits in the Kumano region of Wakayama Prefecture, along the route of the Kumano Kodō pilgrimage trails. The settlement clusters along the Ōtō River, where geothermal water rises through the riverbed at temperatures reaching 70°C. In winter, a large communal bathing pool called Sennin-buro — the thousand-person bath — is constructed in the riverbed using boulders and gravel. The surrounding area forms part of the UNESCO-listed Sacred Sites and Pilgrimage Routes in the Kii Mountain Range. Hongu Taisha, one of the three grand Kumano shrines, lies a short drive upriver, with its original site at Ōyunohara marked by the largest torii gate in Japan at over 33 metres tall.
Family
Children dig their own hot spring pools in the riverbed — it is essentially a geothermal sandpit. The novelty never wears off, and the Kumano Kodō's shorter trails are manageable for young walkers.
Friends
Building your own riverside onsen as a group, soaking under stars, and hiking the Kumano Kodō by day creates the kind of trip friends retell for years.
Couple
A private riverside bath dug by hand, a ryokan dinner, and the spiritual gravity of the Kumano shrines give Kawayu an intimacy that manufactured onsen resorts cannot replicate.
Mehari-zushi rice balls wrapped in pickled mustard leaves, the Kumano pilgrim snack.
Sanma Pacific saury grilled whole at riverside ryokan in autumn.

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