Spas with thermal pool

Palm Springs, California

Adults-only hot springs resort on Miracle Hill in Desert Hot Springs with private mineral tubs, a Finnish sauna, salt room and 35 spa treatments.

Tuscany

Hotel spa inside Florence's Four Seasons, with a walled garden pool, whirlpool, sauna, steam room and couples suite, open to day-pass guests.

Duluth, Georgia

A 24-hour Korean bathhouse in Duluth with a $30 day pass, sauna rooms, cold plunge, thermal circuits and a junior Olympic pool.

Tucson, Arizona

Adults-only hotel spa at El Conquistador Tucson with a salt therapy lounge, heated outdoor pool and mountain views, day passes available to hotel guests.

Napa Valley, California

Adults-only resort spa in Napa Valley with pools, sauna, steam and a fitness center, open to hotel guests and club members via day pass.