Spas with upscale

Chicago, Illinois

Thermal baths and spa rituals in a restored 1902 factory in West Town, Chicago, open daily for adults-only soaking and massage packages.

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.

Santa Fe, New Mexico

A small medical spa in Santa Fe focused on advanced facials, skin rejuvenation and massage, by reservation.

Barcelona, Catalonia

Adults-only thermal baths in a converted 18th-century building near Barcelona's Born market, with soaking pools, massages and couples rituals.

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.

Sonoma, California

A Sonoma medical day spa run by a 25-year skincare specialist, offering non-toxic facials, microcurrent and micro-channeling treatments up to $350.

Minneapolis, Minnesota

Hotel spa inside Hotel Ivy in downtown Minneapolis, offering massages, facials, body treatments and a steam room on the hotel's second floor.

Washington, D.C., District of Columbia

Hotel spa inside the Watergate Hotel with a retro indoor pool, whirlpool, dry sauna and steam room, plus a day pass for treatments and amenities.

Aspen, Colorado

A reservation-only Aspen studio offering private sound, energy and subconscious-journey sessions instead of classic spa treatments.

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.

Nashville, Tennessee

Upscale hotel spa inside 1 Hotel Nashville with 38 treatments, an infrared sauna wrap, and an 18-plus minimum age; no day pass offered.

Boston, Massachusetts

A Newbury Street day spa and med spa in Back Bay offering massage, facials, hydrafacials and microneedling, closed Mondays.

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.

Prague

A day spa near Wenceslas Square in Nové Město offering massages, facials and thermal pool access with day passes for walk-ins.

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.

Asheville, North Carolina

Medical spa in Asheville offering injectables, PRP microneedling, red light therapy and a salt facial, with walk-ins accepted when space allows.

Houston, Texas

Day spa in Houston's Westside with a grotto pool, outdoor pool, steam rooms and sundeck, plus an on-site restaurant; walk-ins welcome.

New York City, New York

A below-street-level day spa in NoHo with thermal baths, a three-story indoor waterfall, sauna, steam room and cold plunge, plus massage and facial treatments.

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.

Doha

Hotel spa at The Westin Doha with some of the city's largest wet facilities, accessible to hotel guests and members only, no day passes sold.

Philadelphia, Pennsylvania

Herb & Gem Spa is a small day spa in South Philadelphia offering massage, facial and reflexology packages with walk-in day passes.

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.