Spas with thermal pool

London, England

Thermal bathhouse near Covent Garden in a former J.M. Barrie house, offering multi-temperature pools, massages and couples treatments by reservation.

Toronto, Ontario

A reservation-only thermal bath circuit in a 1912 Edwardian building in Toronto, with eight pools, a dry sauna, steam room and massage treatments.

Buenos Aires

A hotel spa inside the Palacio Duhau-Park Hyatt in Barrio Norte, open only to hotel guests, with Mapuche-inspired treatments and a semi-olympic pool.

Ainsworth, British Columbia

A lakeside hot springs resort in British Columbia's Kootenays with public thermal pools, a spa, restaurant and overnight rooms, closed Tuesdays.

Barcelona, Catalonia

Adults-only thermal baths in a converted 18th-century building near Barcelona's Born market, with soaking pools, massages and couples rituals.

Bagno Vignoni, Tuscany

Hotel spa in a 15th-century Bagno Vignoni palazzo with a thermal pool fed by the village's natural hot springs, open to day visitors.

Santiago, Santiago Metropolitan

A hotel spa in Macul, Santiago, with thermal pools, sauna, steam room and cold plunge, open to hotel guests only, no day passes offered.

Längenfeld, Tyrol

A large thermal bath and 4-star hotel spa in the Ötztal valley near Längenfeld, with indoor-outdoor pools, a sauna garden and a dedicated kids' water world.

Sydney, New South Wales

Korean bathhouse in Chatswood with herbal baths, steam room and dry sauna, built around the traditional Korean body scrub, open by reservation only.

O Grove, Galicia

A thermal spa on Isla de la Toja combining a seawater hydrotherapy circuit with a mineral-medicinal water balneario, open daily with a day pass option.

Calistoga, California

A moderate-priced resort spa in Calistoga with geothermal mineral pools, open daily 9am-5pm and offering day passes to the public.

Miami, Florida

Day spa in the Sherry Frontenac Hotel's lower lobby in Miami Beach, with sauna, steam, cold plunge and thermal pool alongside massage treatments.

Miami, Florida

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

Kuala Lumpur

An onsen-style day spa in Kampung Baru, Kuala Lumpur, with thermal pools, sauna, steam room and couples treatments.

Napa Valley, California

A boutique day spa in downtown Napa Valley with nine treatment rooms offering massage, facials and body work, plus sauna, steam and a thermal pool.

Plainfield, Indiana

Day spa in Plainfield, IN offering facials, massages and body-sculpting treatments alongside a sauna, steam room and thermal pool, reservation required.

Las Vegas, Nevada

A 134,000-square-foot spa and fitness center inside The Venetian Resort, with over 100 treatments, thermal experiences and day passes for non-guests.

Miami, Florida

A beachfront resort spa in North Beach, Miami with cryotherapy, a floating salt bath, sauna, steam and a cold plunge, open to walk-ins and day-pass guests.

Karlovy Vary, Karlovy Vary Region

A 5-star medical spa and wellness hotel beside Karlovy Vary's colonnades, with seven saunas, five pools and a day pass for non-guests.

Marrakech, Marrakesh-Safi

A 1,200-square-metre hotel spa at Selman Marrakech built around the Chenot method, with hammams, pools and multi-day wellness programmes.

Chicago, Illinois

Adults-only hotel spa in River North with a 67-foot pool, multiple sauna and steam rooms, and day passes for non-guests.

Miami, Florida

Hotel spa inside Dua Miami, Autograph Collection in Brickell, open daily 9am-6pm, with sauna, steam room, cold plunge and couples massage rooms.

Palm Springs, California

Moroccan-themed inn in Desert Hot Springs with natural mineral hot springs, a spring-fed pool and day-pass access from 9am to 4pm.

Monroe, New Jersey

Affordable day spa in Williamstown, NJ with sauna, steam room and thermal pool, offering massages, facials and couples treatments.