Spas with reservation required in United States

Massage-focused day spa in Rocky River offering couples treatments, sauna, steam room and thermal pool, open daily by appointment.

Day spa in Steiner Ranch, Austin, offering sauna, steam room, thermal pools, cold plunge and a signature scalp treatment for adults, open Monday through

A small day spa studio in Castle Rock offering massage, facials, waxing, lashes, brows and permanent cosmetics by appointment.

A moderate-priced day spa in Tucson's Sam Hughes neighborhood offering massage, facials, nails and waxing, with combo spa days from $129 to $315.

Day spa in West Sedona with sauna, steam room and a thermal pool, open daily by reservation and set up for couples treatments.

A themed-suite day spa in Seattle's SODO district offering massages, facials, couples packages and a few overnight suites.

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.

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

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 medical spa in Manhattan built around lymphatic drainage therapy and acupuncture, open daily 10am to 9:30pm.

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

A no-frills massage studio in North Dallas offering Swedish, deep tissue and its own signature treatment, plus in-home and office visits by appointment.

A medical spa in Chicago's Lincoln Park offering Botox, dermal fillers, laser hair removal, IPL and semaglutide weight-loss treatment, priced in the moderate

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.

A no-frills massage and facial day spa on West Flamingo Road in Las Vegas, open daily 10am to 8pm with walk-in and reservation options.

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

Float Horizen is a day spa in Nashville's East End offering sensory-deprivation float tanks, infrared sauna, massage and sound meditation sessions.

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

An adults-only medical day spa in Colorado Springs offering constitutional hydrotherapy, infrared sauna and homeopathy by appointment.

A Thai massage day spa in Honolulu's McCully-Moiliili area offering solo and couples treatments daily from 9am to 11pm.

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

Adults-only day spa in Maplewood, NJ, offering deep tissue massage, bodywork and facials by appointment, open daily 9am-8pm.

Day spa in Richmond's West End with massage, organic facials, HydraFacial, infrared sauna and herbal bath soaks; walk-ins welcome, reservations recommended.

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