Jigoku Onsen Seifuso

Jigoku Onsen is an old toji (湯治, long-stay cure) spot high up inside the Aso caldera, and Seifuso is the inn there. The signature bath is Suzume-no-yu (すずめの湯), a cloudy, sulfur-smelling pool where the water wells up from beneath your feet and goes straight in without dilution. It is a mixed bath, but you wear a bathing garment or swimsuit, so everyone can use it together. The water is murky enough that you can't see the steps, so feel your way in. The other two baths, Moto-no-yu (元の湯) and Tamago-no-yu (たまごの湯), are separate for men and women and have showers. Moto-no-yu has a stone tub dug back out after the debris flow and big timber beams overhead. Tamago-no-yu is newer and more concrete, with a semi-open indoor bath and an open-air bath looking out over Aso. Overnight guests swap the two between men and women each morning and evening. Rooms are in the main house, in lofts and toji rooms, and in detached cottages, each of which has its own semi-open bath. There is also a restaurant, and day visitors can have lunch. The inn was hit by the 2016 Kumamoto earthquake and the debris flow that followed. Suzume-no-yu survived and kept flowing, and the other baths were rebuilt.