Kawayu Onsen

At Kawayu the hot spring comes up through the gravel bed of the Oto river, which means that if you dig a hole in the riverbed it fills with hot water. In summer people do exactly that — the inns lend spades to guests and you make your own bath on the shingle, sized to taste.

From December to the end of February the village goes further and dams a section of the river to make the Senninburo, the thousand-person bath: an open-air pool of about a thousand square metres in the middle of a river valley, free, open from half past six in the morning until ten at night. There is no roof, no wall and no charge. Swimsuits are normal. It is a fifteen-minute drive from Kumano Hongu and it is one of the strangest and best things in Japan.