Spas with thermal pool

Tuscany

Hotel spa inside Florence's Four Seasons, with a walled garden pool, whirlpool, sauna, steam room and couples suite, open to day-pass guests.

Baden-Baden, Baden-Württemberg

A Renaissance-era thermal bathhouse in Baden-Baden built in 1877, offering a structured Roman-Irish bathing ritual for about 39 euros a day.

Temescal Valley, California

Adults-only hot springs resort in Temescal Valley with 19 outdoor mineral pools, red clay baths, and a cave-like grotto, open daily 9:30am-5pm.

The Hamptons, New York

Oceanfront resort spa in Montauk with a seawater and marine-based treatment menu, hydrotherapy, contrast bathing, and a heated saltwater pool.

Hakone, Kanagawa

Day-use hot spring in Tōnosawa, Hakone, styled like an old farmhouse village, with communal baths and 19 private open-air rental baths.

Tucson, Arizona

A resort spa in Tucson's Starr Pass area with a saline lap pool, sauna and fitness center, plus signature treatments from $159 for hotel guests.

Mallorca, Balearic Islands

A clifftop luxury hotel spa near Cas Català-Illetes with an infinity pool, relaxation pool and a seasonal Spa Bodyna, open to day visitors as well as guests.

Opatija, Primorje-Gorski Kotar

A 5-star hotel spa in Opatija with a sauna centre, seawater pools and couples treatments, open only to Hotel Ambasador guests.

Krynica-Zdrój, Lesser Poland

Mountain resort spa in Krynica-Zdrój with indoor and outdoor pools, a sauna complex, and a clothing-optional 18+ zone; day passes available.

Hot Springs, Arkansas

A nine-suite boutique hotel on Bathhouse Row with in-room soaking tubs fed by hot spring mineral water, open only to overnight guests.

Portorož, Coastal-Karst

Hotel spa on Portorož's seafront promenade with heated seawater and thermomineral pools, open to day visitors as well as hotel guests.

Valle de Bravo, State of Mexico

A forest hotel spa outside Valle de Bravo built around a hydrotherapy circuit of hammam, sauna, cold pool and contrast pools, open to overnight guests only.

Velingrad, Pazardzhik

Hotel spa in Velingrad with mineral-water pools, saunas, steam rooms and a hammam spread over 4,000 square metres; day passes are available.

Houston, Texas

Upscale day spa at The Houstonian in Houston with 22 treatment rooms, soaking pools and a sundeck; pool access comes with a 50-minute-plus treatment, not a

Bük, Vas

Hotel spa in Bükfürdő with pool, jacuzzi, saunas and massage services, open to guests staying in either of its two linked wings.

Zurich

Thermal baths and rooftop infinity pool set in a former Zurich brewery's historic vaults, with a Roman-Irish spa ritual and day-pass access.

Duluth, Georgia

A 24-hour Korean bathhouse in Duluth with a $30 day pass, sauna rooms, cold plunge, thermal circuits and a junior Olympic pool.

Bursa

A historic thermal bathhouse and small hotel in Bursa's Kükürtlü district, with separate men's and women's hamams, day passes, and overnight stays.

Bishop, California

A century-old natural hot springs pool near Bishop in the Eastern Sierra, with a cooling waterfall, a separate hot soak, and simple day-use facilities.

Lake Como, Lombardy

A day spa inside the Castello di Casiglio parkland near Erba, offering a 3-hour pass with heated indoor-outdoor pools, saunas and a Turkish bath; adults and

Tucson, Arizona

Hotel spa at the Westin La Paloma Resort in Tucson offering massages, facials and body treatments, open only to resort guests.

Scottsdale, Arizona

Adults-only hotel spa at The Scott in Scottsdale with six treatment rooms, sauna, steam and pools, plus day passes for non-guests.

Orlando, Florida

Family resort near Walt Disney World with a pirate-themed pool complex and a spa offering day passes and couples treatments.

Austin, Texas

Lakeside day spa near Austin offering a $150 day pass with pools, steam room, sauna and relaxation lounges, open daily 9am–9pm.