Beppu is not a single hot spring but hundreds, gathered along the eastern slope of two volcanoes — Tsurumi and Garandake — and spilling down toward the sea. The numbers are difficult to absorb: more sources than anywhere else in Japan, more volume, more visitors — eight million a year, the data says. Yet numbers do not capture what it feels like to walk through a city where steam rises from drains and gutters, from hillsides and parking lots, as though the ground itself were exhaling. The eight districts that give the place its name — Beppu Hatto — each carry a different character, a different water, a different reason for being. This is not one destination but a loose constellation, and the visitor who stays long enough begins to sense the distinctions.

Kannawa, up on the hillside, is the one that pulls toward something older. It was designated a national health resort in 1985, and it still carries the quieter atmosphere of tōji — the long therapeutic stay. Steam drifts visibly across the rooftops there. Myōban, higher still, has produced yunohana — mineral deposits harvested from the vapors — since the Edo period, a craft recognized as an intangible folk cultural property. Down near the station, the main Beppu district is busier, more convivial, shaped by decades of resort-town commerce. Hamawaki grew around a shrine gate. Each neighborhood answers a different mood.

What might it feel like to stay several nights? Perhaps like settling into a city that has never quite decided whether it is a pleasure quarter or a clinic, an industrial site or a geological wonder. Beppu appears in the Bungo no Kuni Fudoki, in the Man'yōshū; it hosted Japan's first geothermal power generation in 1925; Kyoto University built a research facility here to study the earth's heat. The ferries still arrive from Osaka. The steam still rises. There is something almost matter-of-fact about the abundance — water everywhere, heat everywhere, the ordinary business of a city that happens to sit on top of a volcano and has been negotiating that fact for a very long time.