Spas with private suites

San Diego, California

Adults-only hotel spa at Kona Kai Resort on Shelter Island with six treatment rooms, a couples' suite and day-pass access for non-guests.

Miami, Florida

A 12,000-square-foot hotel spa at Coral Gables' Biltmore, with eucalyptus steam rooms, Himalayan salt saunas and a couples suite; adults-only, reservation

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.

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.

Los Angeles, California

Downtown LA hotel spa at the Ritz-Carlton with massages, facials, a couples suite, rooftop pool and gym; outside guests need to book a treatment to enter.

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.

Calistoga, California

Hotel spa in downtown Healdsburg with a garden patio, jacuzzi and pool access, open daily 9am-5pm for guests and day visitors.

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.

Palm Springs, California

A 38,000-square-foot resort spa at JW Marriott Desert Springs in Palm Desert offers day passes, saunas, a saltwater lap pool and couples suites.

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.

Denver, Colorado

A hotel spa in downtown Denver with a $150 day pass covering pool, steam room, whirlpool and fitness centre access, open to non-guests.

Houston, Texas

A Four Seasons hotel spa in downtown Houston with three treatment rooms, a couples' suite and rooftop pool access, open to day-pass guests.

Orlando, Florida

Adults-only resort spa at Four Seasons Orlando, open daily 9am-8pm, with 12 treatments, couples' suites and access to a 21+ pool for guests booking a 50-minute

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.

Boston, Massachusetts

A luxury hotel spa in Boston's Back Bay with a Crystal Steam Room, Vitality Pool and private couples suites, open to adults 18 and over.

Aspen, Colorado

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

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.

Boston, Massachusetts

Hotel spa inside the Four Seasons One Dalton in Back Bay, with six treatments, a couples' suite and a 64-foot lap pool, open to hotel guests.

Miami, Florida

Hotel spa at The Setai in Miami Beach with 7 ocean-view treatment rooms, 5 couples suites, saunas, steam and a cold plunge.

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.

The Colony, Texas

A day-soaking spa in The Colony with mineral pools at varying temperatures, seven saunas, cold plunges and a poolside café.

Aspen, Colorado

A compact hotel spa inside Hotel Jerome in downtown Aspen, with three treatment rooms and a co-ed relaxation lounge, open daily 9:30am–5:30pm.