Spas with reservation required

San Francisco, California

Adults-only Russian bathhouse in San Francisco's India Basin with steam rooms, cold plunge, rooftop deck and a café, open daily except Tuesday.

Palm Springs, California

Hotel spa inside the Avalon in Palm Springs, open Thursday through Monday, with a $75 day pass covering jacuzzi, sauna, cold plunge and steam rooms.

Boston, Massachusetts

A Finnish kelo-log banya in Newton with sauna, steam room and cold plunge, alternating men's and women's days, day passes from $69.

Chicago, Illinois

Hotel spa on the lower level of the Fairmont Chicago, open to guests for massages, facials and a couples suite with an infinity-edge soaking tub.

San Francisco, California

Hotel spa at The Huntington Hotel on Nob Hill with a heated soaking pool, sauna, steam room and terrace, open daily 8am-7pm; treatment booking required.

Palm Springs, California

Adults-only hotel spa at the Parker Palm Springs with 15 private treatment rooms, couples suites and a $300 signature aloe treatment.

Park City, Utah

A 14-room hotel spa at Westgate Park City Resort with a waterfall, sauna, steam room and thermal pools, open daily 9:30am-6:30pm.

Scottsdale, Arizona

Hotel spa at the Inn at Eagle Mountain in Fountain Hills with sauna, steam room, pools and a $69 60-minute massage as its signature treatment.

Las Vegas, Nevada

Adults-only hotel spa inside Westgate Las Vegas offering massages, facials, salon services, sauna, steam room and a thermal pool, open daily 9am-6pm.

Palm Springs, California

Adults-only hotel spa at Tommy Bahama Miramonte in Indian Wells with 15 treatments, eucalyptus steam rooms, a hydrotherapy jacuzzi and saltwater pool.

Calistoga, California

Spa Talisa is the adults-only spa at the Four Seasons Resort Napa Valley in Calistoga, with vineyard-view gardens, barrel saunas and a sunken whirlpool for

Palm Springs, California

Hotel spa at Agua Caliente Rancho Mirage with day passes for the sauna, steam room, salt rooms and private spa pool.

Marana, Arizona

Adults-only hotel spa at Dove Mountain Resort in Marana with desert-themed treatments, an infinity-edge pool, sauna and steam room; facility access comes with

Napa Valley, California

Adults-only hotel spa in Napa Valley with a co-ed thermal circuit of sauna, steam room and cold shower, open daily 10am–6pm; day passes available.

Tucson, Arizona

Six-room hotel spa at Hacienda del Sol in Tucson, open daily 9-6, taking both resort guests and local walk-ins for massages, facials and body treatments.

Napa Valley, California

Adults-only hotel spa in downtown Napa with thermal circuits, sauna, steam and cold plunge, plus massages, facials and medical aesthetics.

Calistoga, California

A 20-treatment hotel day spa in Santa Rosa with an indoor caldarium plunge pool, eucalyptus steam rooms, and walk-in or reserved day passes for adults 18+.

Scottsdale, Arizona

Hotel spa inside Hotel Solaya in South Scottsdale built around Tod Miller's proprietary BodyWalking compression technique, with four treatments and a $335

Palm Springs, California

A 16-room adults-only hotel in Desert Hot Springs with three natural mineral-water pools fed by a 350-foot geothermal well, plus a small on-site spa and

Scottsdale, Arizona

Adults-only hotel spa at the Fairmont Scottsdale Princess with a rooftop pool, grotto waterfall pool, sauna, steam room and cold plunge, open daily 6am-7pm.

Sonoma, California

Hotel spa at The Lodge at Sonoma with an outdoor terrace, soaking pool, plunge pool and barrel sauna, open daily 9am-5pm, adults-only, reservation required.

Los Angeles, California

A hotel spa at the Conrad Los Angeles in Downtown LA, open only to hotel guests by reservation, with an adults-only, couples-friendly setting.

Albuquerque, New Mexico

Hotel Zazz is an adults-only boutique hotel in Albuquerque's Nob Hill district with an on-site spa, heated pool and speakeasy lounge.

Sedona, Arizona

A hotel spa inside a Mission/Arts & Crafts style bed and breakfast inn in Sedona's Red Rock Country, open daily 9am–5pm by reservation.