Spas with thermal pool

Calistoga, California

A historic hot-springs resort in Calistoga with an early-1900s mineral pool, mud baths, and a public restaurant, but spa access is limited to hotel guests.

Miami, Florida

A hotel spa in downtown Miami with a day pass covering sauna, steam, cold plunge and thermal pools, plus 13 treatments on the menu.

San Juan

Adults-only hotel spa inside La Concha Resort in Condado, San Juan, offering couples massages and a small treatment menu for guests 18 and up.

Austin, Texas

Adults-only resort spa on Lake Austin offering all-inclusive overnight stays and limited day passes to pools, saunas, steam rooms and lake activities.

New Orleans, Louisiana

Hotel spa and rooftop wellness deck in New Orleans' CBD with sauna, steam, cold plunge and thermal circuits, restricted to guests 21 and up.

Karjalohja, Uusimaa

Lakeside resort spa on Lohjanjärvi in Karjalohja, about an hour from Helsinki, with a day pass, thermal pool, salt room and restaurant.

Miami, Florida

Hotel spa deck in downtown Miami with sauna, steam room, cold plunge and thermal pools overlooking Biscayne Bay, day passes from $50.

Hudson Valley, New York

Resort spa at Mohonk Mountain House with a steam room, sauna and outdoor heated mineral pool, open to overnight guests and day-pass visitors.

San Francisco, California

An adults-only bathhouse in San Francisco's Tenderloin with a thermal pool and an on-site restaurant, open daily except Tuesdays.

New York City, New York

Adults-only day spa on Governors Island with heated outdoor pools, saunas and an Italian-style café, reachable by ferry from Manhattan.

Pamukkale, Denizli

A 315-room thermal resort in Karahayıt near Pamukkale with its own thermal pools, pine-shaded gardens and on-site dining, open to hotel guests only.

Bangkok

Hotel spa at SO/ Bangkok on Sathorn Road offering facial, body and beauty treatments plus rooftop infinity pool and fitness access, hotel guests only.

Shibu Onsen, Nagano

A ryokan in Shibu Onsen with indoor and outdoor hot-spring baths fed by two blended mineral springs, open only to overnight guests.

Scottsdale, Arizona

A luxury resort spa in Paradise Valley near Scottsdale with outdoor baths, a thermal pool and a relaxation lounge, open to hotel guests only.

Scottsdale, Arizona

An adults-only hotel spa in Old Town Scottsdale with sauna, steam room, cold plunge and thermal pools, open to hotel guests 21 and up.

The Hamptons, New York

Adults-only destination spa and 12-room retreat in Water Mill, offering hydrotherapy, yoga, spa treatments and overnight stays by reservation.

Tyrol, Bavaria

Hotel spa in Kreuth-Reitrain near Tegernsee with a 3,000 sqm onsen-style bathing area, hot and cold pools, saltwater pools and sauna, open on a day-pass basis.

Lake Tahoe, California

Hotel-only spa at a lakefront resort in South Lake Tahoe, with an outdoor heated pool, Jacuzzi and treatment rooms aimed at couples.

Miami, Florida

A large hotel wellness resort on North Beach with a European-style hydrotherapy circuit, cryotherapy, acupuncture and an oceanfront fitness center.

Phoenix, Arizona

Adults-only hotel wellness setup in downtown Phoenix with a heated pool, sauna and steam room, day passes available for $50.

Ischia, Campania

A day-pass thermal park in Serrara Fontana on Ischia with multiple pools, a restaurant, and family-friendly access, open daily 9am to 6pm.

Tucson, Arizona

A hotel spa at an 80-acre Sonoran Desert resort in Tucson, open to overnight guests, with three pools, hot tubs, sauna and yoga classes.

Buxton, England

A hotel spa built into Buxton's historic Crescent, centred on a thermal pool, hydrotherapy circuit and salt room, open to hotel guests only.

Ubud, Bali

A 22-acre riverine-forest wellness retreat outside Ubud built around a sacred spring, accessible only to guests staying at the estate.