Spas with reservation required

Saturnia, Tuscany

Walk-in thermal park in the Maremma countryside with four outdoor sulfur pools, hydromassage jets and a vascular circuit fed by a 3,000-year-old spring.

Hudson, New York

Adults-only communal thermal baths and steam room in downtown Hudson, NY, with day passes, memberships and treatment-plus-soak packages.

Shibu Onsen, Nagano

Reservation-only private hot spring and sauna suites at a Nagano brewery complex, built around a craft beer bathing plan for two to four guests.

Washington, D.C., District of Columbia

A Georgetown studio in Washington, D.C. offering private infrared sauna cabins and float therapy suites, bookable by reservation only.

Birmingham, Michigan

A Birmingham, Michigan day spa built around waterless volcanic rock treatments, with V-steam, facials, massage and a steam room for adults and couples.

Aspen, Colorado

Adults-only hotel spa at The St. Regis Aspen with Thai-inspired massage, 111Skin facials, an AI robotic massage, and a day pass covering pool, cold plunge, and

Denver, Colorado

A 14,000-square-foot hotel spa inside Gaylord Rockies in Aurora, offering massages, facials, body treatments and a couples room, adults only.

Nashville, Tennessee

A Midtown Nashville wellness studio built around cryotherapy, infrared sauna, red light therapy, IV drips and recovery treatments, run mostly through monthly

Dallas, Texas

A membership-based recovery studio in Dallas's Cityplace offering cryotherapy, infrared sauna, compression, IV drips and skin treatments by reservation only.

Nashville, Tennessee

Day spa and medical spa on the third floor of The Westin Nashville downtown, with nine treatment rooms, a dry cedar sauna, steam showers and walk-in access to

Nashville, Tennessee

A community sauna studio in East Nashville's Porter Road corridor with communal and private sauna rooms plus an outdoor pop-up cold plunge.

Budapest

A centuries-old Turkish-style thermal bath on the Buda riverside with pools, saunas, massages and weekend late-night soaking hours.

Sofia, Sofia City

Small day spa near South Park with a heated pool, jacuzzi, Finnish sauna, steam room and a traditional-style hamam, capped at 10 guests.

Sierraville, California

A non-profit hot springs retreat near Lake Tahoe with natural spring pools, reservation-only day and evening soaks, camping and rooms, closed Mondays and

Kyoto

Hotel spa in Kyoto's Higashiyama Ward with a day pass for pool, bathhouse, sauna and gym, plus treatment suites and couples options.

Boston, Massachusetts

A Newbury Street medical spa for injectables, laser hair removal, microneedling and facials, with massage also on the menu, by appointment only.

Seattle, Washington

A reservation-only social wellness sauna spa in Renton (serving the Seattle area) with a thermal pool, cold plunge, sauna and steam room, day passes from $75.

Austin, Texas

Adults-only hotel spa at the Fairmont Austin with nine treatment rooms, a hydrotherapy circuit, sauna and cold plunge, open daily with day passes available.

Carmel-by-the-Sea, California

Resort spa at Carmel Valley Ranch with 12 treatment rooms, private terraces, a saltwater pool and infinity hot tub, open to adults by reservation.

San Diego, California

Adults-only day spa at Mission Bay Resort with massage, facials, Himalayan salt treatments and couples suites; walk-ins and day passes welcome.

Palm Springs, California

Hotel spa at the Renaissance Esmeralda in Indian Wells offering desert-inspired treatments, a recovery lounge, steam rooms and day passes, adults only.

Piešťany, Trnava Region

Spa Irma on Piešťany's spa island offers historic mud and mirror thermal pools, a hydrotherapy circuit and a 60-treatment medical spa menu, adults only.

Boca Raton, Florida

Hotel spa at The Boca Raton with 44 treatment rooms, a spa pool and waterfall whirlpools, open to resort guests, club members and day-pass visitors by

Austin, Texas

Hotel spa at Hotel Viata in West Lake Hills with treatment rooms, a couples suite, pool, sauna, steam room and a day-pass option for amenity access.