Onsen

Onsen are natural hot springs, and Japan has one of the highest concentrations of geothermal activity in the world — a legacy of the same volcanism that produces its mountains — so hot spring towns cluster wherever that geology surfaces, from coastal Kyushu to the Hakone caldera outside Tokyo. Bathing is communal and, at almost all traditional facilities, done nude and gender-separated; swimwear is not worn in the bath itself.

The universal rule is to wash and rinse thoroughly at the shower stations before entering the bath — the water is shared, not for washing in. Long hair should be tied up and kept out of the water, and the small hand towel provided is for modesty on the walk to the bath, not for use inside it. One point of friction for visitors: many traditional onsen still refuse entry to anyone with a visible tattoo, a legacy of the tattoo's association with organized crime, though this is loosening, especially at hotel and resort baths that offer private tattoo-friendly bookings or rental rooms (kashikiri-buro).

Onsen towns are usually built around ryokan (traditional inns) that pair the bath with a kaiseki dinner and a night in a tatami room, but many also operate day-use bathhouses (higaeri onsen) for visitors just passing through. The heaviest concentrations are in Kyushu (Beppu, Yufuin, Kurokawa), Tohoku and Gunma's mountain onsen towns, Hakone and the Izu Peninsula near Tokyo, and volcanic Hokkaido.