Spas with reservation required

New York City, New York

Thermal bath circuit and massages in a restored 1883 Tribeca textile factory, with a skylit tepidarium and candlelit thermal pools; reservation required.

Coorg, Karnataka

Riverside resort spa in Coorg with private bungalows, a pool, and spa treatments along the Kaveri River; booking required.

Rishikesh, Uttarakhand

An upscale riverside resort 18 km outside Rishikesh with an in-house spa, yoga studio and restaurant, open only to overnight guests by reservation.

Naples, Florida

Sole-practitioner day spa in Naples, FL offering massage, cupping, facials and a plumbed Japanese-style head spa, with private treatment suites.

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.

Mérida, Yucatán

Resort spa on the grounds of Hacienda Xcanatun near Mérida, with a pavilion over a pond offering Asian-style massages and facials by reservation.

Scottsdale, Arizona

Hammam-inspired hotel spa at Omni Scottsdale Resort & Spa at Montelucia in Paradise Valley, with private suites and massage, facial and body treatments for

Baños, Tungurahua

Day spa in Baños with 46 treatments, 11 themed rooms, and skincare made from garden-grown herbs, fruit and volcanic ash.

Sonoma, California

A moderate-priced day spa a block off Sonoma Plaza offering massage and facials from a certified therapist and licensed esthetician, with private treatment

Vail, Colorado

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

Miami, Florida

A Brickell medical spa running 18 categories of non-invasive aesthetic treatments, including Botox, fillers and a signature facial, weekdays only.

Punta Cana, La Altagracia

Upscale day spa in Punta Cana offering massages, facials, a thermal pool and ocean-view relaxation lounges, open daily 9am-7pm.

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

Asheville, North Carolina

Ayurvedic destination retreat in the Blue Ridge Mountains near Asheville, with day-pass spa visits and multi-night panchakarma cleanses by reservation.

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.

Charlotte, North Carolina

A moderate-priced day spa in Charlotte's SouthPark area with a sauna, steam room and thermal pool alongside massage, facial and body-treatment menus.

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.

San Diego, California

A budget-friendly massage and medspa in Core-Columbia, San Diego, with private suites, a sauna and a couples treatment room.

Vichy, Auvergne-Rhône-Alpes

Adults-only thermal baths in Vichy using the town's mineral spring water, with a hydrotherapy circuit and thermal pool, booking required.