Spas with hot tub

San Francisco, California

A San Mateo day spa with a hot tub, open daily 10am-9pm, taking both walk-ins and reservations for couples or solo visits.

New York City, New York

A small Japanese-style bathhouse near Union Square with sauna, hot-tub onsen, cold plunge and a recovery lounge, open by reservation only.

Calistoga, California

A 25-room Sonoma hotel in Forestville with a spa barn offering sauna, steam and pools, mainly for overnight guests.

Asheville, North Carolina

An overnight-stay forest retreat near Fairview with private cedar hot tubs and a shared sauna pavilion session, not a drop-in day spa.

Taos, New Mexico

A moderate-priced day spa at Taos Ski Valley with a heated pool, hot tubs, steam rooms and a day pass open to non-hotel guests.

Denver, Colorado

Adults-only bathhouse on West Colfax Ave in Denver with a steam room, sauna, hot tub and relaxation lounge, open daily except Tuesday.