Spas with thermal pool

Las Vegas, Nevada

Adults-only hotel spa inside ARIA Resort & Casino in Las Vegas, with sauna, steam room, thermal pools and cold plunge, open to hotel guests 18 and up.

Amsterdam, North Holland

A day spa inside a former bank vault in central Amsterdam, with pool, whirlpool and a canal-view gym; adults-only, day pass by reservation.

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.

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.

Amman

A hotel hammam in Tla al-Ali, Amman, with marble bathing halls, a hot pool, sauna and Jacuzzi, offering about 20 treatments from a basic scrub to a $120

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.

Chiang Mai

Hotel spa at Anantara Chiang Mai with steam rooms, sauna and couples' suites, built around the signature Lanna Ritual massage overlooking the riverfront pool.

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.

Hot Springs, Arkansas

Adults-only hotel spa at Oaklawn Resort in Hot Springs with vitality pools, heated loungers, needle showers and treatment-based access only.

Las Vegas, Nevada

Adults-only hotel spa at Resorts World Las Vegas with a six-pool hydrotherapy circuit, salt room, and a themed Aufguss sauna show on weekends.

Palm Springs, California

Adults-only hot springs resort on Miracle Hill in Desert Hot Springs with private mineral tubs, a Finnish sauna, salt room and 35 spa treatments.

Tenerife, Canary Islands

A hotel spa at Bahía del Duque in Costa Adeje with an outdoor seawater thalassotherapy circuit, hammam, saunas and a cold plunge, open to day visitors.

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.

Banff, Alberta

A historic outdoor mineral pool run by Parks Canada on Sulphur Mountain in Banff, open daily and walk-in only, no reservations.

Doha

Hotel spa inside Banyan Tree Doha with separate men's and women's hydrothermal suites, open daily 10am-11pm to hotel guests only.

Calistoga, California

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

Beppu, Oita

A budget mineral-mud and colloid hot-spring bathhouse in the Myoban district of Beppu, open daily for walk-in day soaks or an overnight stay.

Los Angeles, California

A clothing-optional Korean-style bathhouse in East Hollywood built over LA's only natural mineral hot spring, with soak pools, steam room and sauna.

Kuala Lumpur

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

Hot Springs, Arkansas

Historic 1912 bathhouse on Bathhouse Row offering walk-in thermal mineral baths, steam cabinet and Swedish massage, no appointment needed.

Ourense, Galicia

Riverside hot springs in Ourense with a Japanese-inspired design, day pass 6.95 EUR, minimum age 5, closed Tuesdays.

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.

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.