Spas with reservation required

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.

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.

Scottsdale, Arizona

North Scottsdale day spa with massage, facials, sauna, steam and a thermal pool, plus private suites for couples and groups.

Palm Springs, California

A no-frills, family-run day spa on Indian Canyon Dr offering walk-in massage and foot reflexology from $40, open daily until 10pm.

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.

Milford, Ohio

A small, adults-only day spa in Historic Old Milford with a salt room, massage room and red light therapy, booked by reservation.

Seattle, Washington

An adults-only wellness studio near Green Lake with private infrared sauna suites, therapeutic massage and red light therapy by reservation.

Napa Valley, California

Adults-only resort spa built into a wine cave in Napa, with a vineyard-view pool, sauna, steam room and hot tub; reservations required.

Chicago, Illinois

A moderately priced day spa in Chicago's Lakeview neighborhood focused on Chinese-style head and scalp treatments, open to adults 16 and up.

Minneapolis, Minnesota

A St. Paul wellness studio in Macalester-Groveland offering infrared sauna, float tanks, salt therapy and cold plunge by reservation, adults-only, day-pass

Colorado Springs, Colorado

A moderate-priced holistic wellness center in West Colorado Springs offering dry salt therapy, massage, yoga and occasional sound-healing or cacao ceremonies.

Tampa, Florida

Adult-focused day spa in North Tampa offering facials, massage, waxing, infrared sauna and salt therapy, open daily with walk-ins welcome.

Koh Samui, Surat Thani

Kamalaya Koh Samui is an adults-only destination spa and wellness retreat on Laem-Set Rd with over 100 treatments, thermal circuits and multi-day health

Elkridge, Maryland

A halotherapy day spa in West Elkridge, near Baltimore, built around a salt cave, massage rooms and a yoga studio, aimed at solo adult visitors.

Palm Springs, California

Downtown Palm Springs day spa built around a natural hot mineral spring, with private mineral baths, sauna, steam room and massage.

Springboro, Ohio

A wellness center in Springboro, Ohio built around a natural salt cave, with energy healing, sound baths and metaphysical classes for individuals or groups.

Ubud, Bali

An adults-only wellness retreat on Ubud's Ayung River offering multi-day healing programmes, thermal circuits and plant-based cuisine by reservation only.

San Diego, California

A Clairemont wellness studio in San Diego pairing acupuncture and bodywork with an infrared sauna and a Himalayan salt room for classes.

Transylvania County, North Carolina

All-inclusive multi-night wellness retreat in Pisgah Forest, NC, combining fitness classes, spa treatments, guided hikes and farm-to-table meals in private

Carmichael, California

A single-room salt cave in a Carmichael strip mall offering 45-minute salt therapy sessions for relaxation and respiratory relief.

North Royalton, Ohio

A North Royalton day spa built around a salt room and sauna, with adults-only halotherapy sessions on a walk-in or reserved basis.