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.

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.

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.

Doha

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

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.

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.

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.

Tucson, Arizona

A luxury all-inclusive wellness resort in Tucson's Hidden Valley with four pools, a hydrotherapy circuit, cold plunges and over 200 spa treatments.

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.

Riviera Maya, Quintana Roo

Adults-only hotel spa at Devossion by Live Aqua in Playa del Carmen, open daily 8am-8pm, with sauna, steam room and pools for resort guests.

Da Nang

A Korean-style bathhouse and onsen complex in Da Nang's Hoa Xuan area, with hot spring baths, 11 sauna rooms, massage and a riverside restaurant.

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.