Kuju Kanko Hotel

Set in Aso-Kuju National Park, this hotel taps the Makino-to Onsen (牧の戸温泉) sulfur spring. The water is clear with a faint sulfur scent, gentle enough that bathers describe it as easy on the skin. There are separate indoor and outdoor baths for men and women, and the outdoor bath sits close enough to the mountains that you feel the elevation. Hikers finishing routes on the Kuju range are the main crowd, though day visitors are welcome too.