Spas with reservation required

A luxury day-pass wellness circuit inside Carillon Miami Wellness Resort, with sauna, steam, cold plunge and thermal pools in North Beach.

Day spa in Sacramento's Oak Park with float rooms, private cold plunge and sauna suites, infrared sauna, and a Somadome meditation pod.

Day spa in Allisonville, Indianapolis with sauna, steam room, thermal pool and cold plunge, plus about 10 massage and facial treatments for solo visits or

An upscale day spa on Miracle Mile in Coral Gables with sauna, steam room and cold plunge, known for a $200 signature treatment and couples packages.

Day spa in Columbia-Tusculum, Cincinnati, with massage, facials, an infrared/Himalayan salt sauna and a $99 signature sampler package.

A Houston day spa near Memorial Park offering massage, facials and spa packages, with a sauna, steam room and pool on site.

A moderate-priced day spa in northwest Indianapolis offering float therapy, salt room sessions, infrared sauna, cold plunge and foot detox, closed Mondays.

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.

A float therapy studio in Alexandria offering sensory-deprivation floats, sauna, cold plunge, and red light therapy sessions.

A moderate-priced day spa in Bellevue's Wilburton area offering full-body massage and foot reflexology alongside a sauna, steam room and cold plunge.

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

A reservation-based day spa in downtown Santa Barbara built around private infrared sauna, salt room and cold plunge sessions.

A West Town day spa built around a beer soak, with sauna, steam room, salt room and thermal pool for couples or solo visits.

A Mount Pleasant recovery studio near Charleston offering cryotherapy, compression therapy and infrared sauna sessions, open daily except Sunday.

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.

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

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

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

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

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

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

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