Spas with hotel guests only in Japan

Sapporo, Hokkaido

Natural hot spring inside Sapporo's Jasmac Plaza Hotel in Susukino, open to day visitors and hotel guests alike, with sauna and a rest lounge.

Shibu Onsen, Nagano

A ryokan in Shibu Onsen with indoor and outdoor hot-spring baths fed by two blended mineral springs, open only to overnight guests.

Kamijima, Ehime

An all-inclusive resort on Yugejima island in Setouchi's inland sea, with ocean-view outdoor baths, ocean-front rooms, and a day-pass option.