Spas with reservation required

Taos, New Mexico

Hotel day spa at El Monte Sagrado in Taos with a hydrotherapy circuit, saltwater pool and treatment rooms, open daily, day passes available.

Dallas, Texas

Hotel spa in Uptown Dallas with 12 treatments, couples' rooms, separate men's and women's lounges, sauna, steam room, cold plunge and whirlpool.

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

Lake Tahoe, California

A 17-room, adults-only hotel spa at Lake Tahoe's Ritz-Carlton with a heated lap pool, sauna and steam room; day pass access requires booking a treatment.

Portland, Oregon

Adults-only hotel spa in downtown Portland with a $50 day pass, infinity pool, sauna, steam room and cold plunge shower, booked in advance only.

Palm Beach, Florida

A scalp-focused day spa inside Image Studios on US-1, near the Gardens Mall, offering head spa treatments, facials and couples sessions by appointment.

Wanaka, Otago

A lakefront wood-fired sauna at The Outlet in Wānaka running guided or self-guided group sessions with cold dips in the lake between rounds.

BAITING HOLLO, New York

A 10,000-square-foot spa and hair salon in Baiting Hollow with couple's suites, saunas and steam rooms, part of the East Wind resort on Long Island.

Santa Ynez, California

Adults-only resort spa inside Chumash Casino Resort in Santa Ynez with 21 treatments, a mineral pool, cold plunge and couple's suites.

Scottsdale, Arizona

Resort spa at Camelback Inn in Scottsdale with 20 treatment rooms, a thermal circuit and day-pass access open to non-guests.

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.

Las Vegas, Nevada

An adults-only hotel spa inside Encore Las Vegas with whirlpool, sauna and steam room, open daily for treatments and day passes, walk-ins welcome.

Jackson Hole, Wyoming

A hotel spa at Four Seasons Jackson Hole with treatment suites, whirlpools, a cold tub, salon services and fitness facilities, reservation-only.

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.

Hanmer Springs, Canterbury

Day spa in Hanmer Springs offering massages and facials, with some packages including access to the thermal pools complex next door.

Park City, Utah

A hotel spa in Park City with seven treatment rooms, hydrotherapy tub and steam rooms, open to guests by reservation, minimum age 16.

Bodrum, Muğla

Adults-only hotel spa at Mandarin Oriental, Bodrum with sauna, steam, cold plunge and thermal pools, open daily 10am-10pm, reservation required.

Napa Valley, California

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

Palm Beach, Florida

A 40,000-square-foot day spa at PGA National Resort in Palm Beach Gardens, open to the public, with mineral pools, steam, sauna and a $100 treatment minimum

Chicago, Illinois

A 5th-floor day spa inside the Palmer House Hilton in the Loop, built around a hydrotherapy circuit, Vichy shower treatments and a facial called Glow Revival.

San Diego, California

Resort spa on Mission Bay offering massages, facials and body treatments, with walk-ins welcome and a gym and yoga classes on-site.

Aspen, Colorado

Ski-in/ski-out hotel spa in Aspen with three private treatment suites, 15 treatments, and booking required by phone or email.

Asheville, North Carolina

Adults-only hotel spa in Asheville with a fiber-optic-starred lap pool, waterfall pools, saunas and an electronics-free policy; day passes are limited and

Miami, Florida

Hotel spa at The Ritz-Carlton Key Biscayne, Miami, with treatment suites, sauna, steam room and whirlpool, open to hotel guests 18 and up by appointment.