Spas with reservation required

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.

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.

Park City, Utah

A ten-treatment-room spa inside the private Promontory Club in Park City, with a full hydrotherapy circuit of steam, sauna and cold plunge.

Dublin, Leinster

An outdoor barrel sauna and cold plunge pool setup in Saggart, Dublin, booked in 50-minute sessions for groups and couples.

Cotswolds, England

A wood-fired riverside sauna at Whichford Mill in the Cotswolds, with a cold-plunge bath, river dipping, and both private and communal sessions.

Catskills, New York

A small storefront in Catskill, NY offering whole-body cryotherapy, infrared sauna and red light therapy sessions, open most days except Tuesday and Wednesday.

Carmel, Indiana

A no-frills contrast therapy studio in Carmel, Indiana, built around a 30-minute sauna-and-cold-plunge circuit for solo visitors.

Milwaukee, Wisconsin

East Town Spa in Milwaukee's Juneau Town combines a full-service salon and med spa with a thermal circuit of sauna, steam, pools and cold plunge.

South Jordan, Utah

A day spa and wellness center in South Jordan, Utah, with a salt room, infrared sauna, cold plunge, float therapy and a yoga studio.

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.

Tucson, Arizona

Day spa in Tucson's La Encantada shopping center with a thermal circuit of sauna, steam room, cold plunge and soaking pools.

Vail, Colorado

A Vail day spa offering customized massages and facials plus a recovery room with infrared sauna, cold plunge and yoga mats.

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.

Santa Barbara, California

A State Street halotherapy spa built around a large underground crystal salt cave, with massage, facials and a relaxation lounge.

Minneapolis, Minnesota

A moderate-priced day spa in Minnetonka with a sauna, steam room, thermal pool and cold plunge, set up for couples and adults-only visits.

Barcelona, Catalonia

Rooftop day spa at Casa Bonay hotel in Eixample with dry sauna, hammam, ice bath and a Japanese ofuro, booked by small-group circuit or free use.

Orlando, Florida

Halotherapy day spa in Orlando's Lake Eola Heights offering salt room sessions, massage and acupuncture, adults only, by reservation.

Carmichael, California

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

Tucson, Arizona

Day spa near Swan Way Park in Tucson with a cedar hot tub, cold plunge, infrared sauna and massage, bookable by reservation for adults only.

Maui, Hawaii

A nine-room resort spa on Maui's Road to Hana offering lomi lomi and lava-stone pōhaku wela massage, plus a eucalyptus steam room and cold plunge.

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.

Las Vegas, Nevada

A Henderson day spa in MacDonald Ranch offering massage, facials and a Himalayan salt lounge, with walk-in and reservation options.

Las Vegas, Nevada

Float tank, massage and salt therapy spot in Peccole Ranch, Las Vegas, open daily with walk-ins accepted alongside bookings.

Ojai, California

A small, independently owned day spa in Ojai offering facials, massage, head spa treatments, infrared sauna and salt therapy.