Spas with thermal pool

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.

Archena, Murcia

A 19th-century thermal hotel in Archena with direct access to a Roman-era spring complex, open to day visitors as well as overnight guests.

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

Reykjavik, Capital Region

Eight oceanfront geothermal pools in Hvalfjörður, 45 minutes from Reykjavík, plus steam baths, a bistro and guest houses for rent.

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.

Wiesbaden, Hesse

A 16+ textile-free thermal bath in central Wiesbaden with Roman-style architecture, saunas, steam rooms and a cold plunge pool.

Bad Kissingen, Bavaria

Thermal bath and sauna park in Bad Kissingen with 10 indoor/outdoor pools, nine saunas and a day pass around €40.

Florence, Tuscany

Hotel spa inside the Helvetia & Bristol in central Florence, with two heated pools, a calidarium, sudatorium and tepidarium, open daily to walk-ins and hotel

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.

Austin, Texas

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

Tucson, Arizona

Hotel spa at Loews Ventana Canyon Resort, Tucson, with eight treatment rooms, an adults-only pool, and a 24-hour fitness center; open daily 9am–6pm.

Miami, Florida

Adults-only hotel spa inside the Fontainebleau Miami Beach with a hydrotherapy circuit, mineral pools and a eucalyptus steam room, open to hotel guests booking

Miami, Florida

Adults-only spa and pool complex inside Loews Miami Beach Hotel, open to hotel guests only, with sauna, steam, cold plunge and thermal circuits.

Ein Bokek, Southern District

Hotel spa on the Dead Sea shore in Ein Bokek with a heated mineral-water pool, sulphur pools, hammam and sauna; day passes open to adults 16 and up.

Loutraki, Peloponnese

Thermal-water spa in Loutraki built on an ancient springs site, with indoor and outdoor pools, sauna, steam room and 32 treatments.

Windermere, England

Resort hotel spa on Lake Windermere's shore with thermal suite, indoor pool, sauna and steam rooms, plus massage and facial treatments.

Philadelphia, Pennsylvania

Northeast Philadelphia day spa on Castor Avenue focused on skin treatments, massage and Venus Legacy body contouring, with sauna, steam and a thermal pool.

Pärnu, Pärnu County

A 193-room medical spa hotel in Pärnu with a pool and sauna complex, salt therapy, physiotherapy and water aerobics, open to day visitors.

Indianapolis, Indiana

Day spa in Allisonville, Indianapolis with sauna, steam room, thermal pool and cold plunge, plus about 10 massage and facial treatments for solo visits or

Monroe, Utah

Natural hot spring pools fed by mineral water in rural Monroe, Utah, open 24/7 with day-pass soaking and funky bus and cabin lodging on site.

Munich, Bavaria

A Jugendstil bathhouse from 1901 in Haidhausen with two swimming halls, a Roman-Irish steam bath and sauna, day pool pass from €5.80.

Längenfeld, Tyrol

A 1,800 m² wellness spa inside an adults-only hotel in Austria's Ötztal valley, with sauna, outdoor pool and treatment rooms for guests only.