Spas with reservation required

Los Cabos, Baja California Sur

A hotel spa at Corazón Cabo Resort offering massages, facials and a hydrotherapy circuit with sauna, steam room and hot tub, no day passes sold.

Kissimmee, Florida

A hotel spa at Margaritaville Resort Orlando in Kissimmee with massages, facials and a Himalayan salt room; open daily, walk-ins welcome.

Palm Springs, California

Hotel spa at Agua Caliente Rancho Mirage with day passes for the sauna, steam room, salt rooms and private spa pool.

Tbilisi

A medical spa in Old Tbilisi built around natural sulfur-mineral water and volcanic mud, operating since 1938, open daily 10am–9pm.

Portland, Oregon

An 18-and-up, clothing-optional spa in Portland's Kerns neighborhood with a salt hot tub, sauna, steam room and cold plunge, reservation required.

Taos, New Mexico

Hotel day spa at El Monte Sagrado in Taos with a hydrotherapy circuit, saltwater pool and treatment rooms, open daily, day passes available.

Los Angeles, California

A Silver Lake day spa with 20 treatments, Thai massage, acupuncture and a salt-infused infrared sauna, open daily 10am-9pm.

Las Vegas, Nevada

A Summerlin day spa centered on Himalayan salt rooms, plus massage, facials and Reiki, open daily 10am-7pm.

Asheville, North Carolina

An appointment-only Asheville spa built around a Himalayan salt cave, booking private salt therapy and massage sessions for up to nine guests at a time.

San Diego, California

Adults-only hotel spa in Carmel Valley with a hydrotherapy circuit, two fireplace lounges, and a $100 day pass covering pools and fitness facilities.

Austin, Texas

A hotel spa in downtown Austin with six treatments, a salt-wall relaxation lounge, eucalyptus steam rooms and a fitness center, open daily by reservation.

Seattle, Washington

Hotel spa in downtown Seattle for Four Seasons guests, with a Himalayan salt wall, steam rooms and a six-treatment adults-only menu.

Park City, Utah

A hotel spa in Park City with seven treatment rooms, hydrotherapy tub and steam rooms, open to guests by reservation, minimum age 16.

Killarney, Munster

A hotel spa in Killarney National Park with an adults-only Vitality Suite of hydrotherapy pool, sauna, steam room and outdoor hot tub.

Chicago, Illinois

A 5th-floor day spa inside the Palmer House Hilton in the Loop, built around a hydrotherapy circuit, Vichy shower treatments and a facial called Glow Revival.

Asheville, North Carolina

Adults-only hotel spa in Asheville with a fiber-optic-starred lap pool, waterfall pools, saunas and an electronics-free policy; day passes are limited and

Houston, Texas

A 20,000-square-foot hotel spa in Houston's Westside offering a biohacking facial machine, hydrotherapy circuit and co-ed relaxation lounge, by appointment

Galway, Connacht

Adults-only hotel spa in Galway with a thermal suite, hydro pool and sauna; day pass runs about €50 and reservations are required.

Taos, New Mexico

A reservation-only wellness studio in Taos offering hyperbaric oxygen, colon hydrotherapy and infrared sauna sessions aimed at altitude recovery.

Miami, Florida

Hotel spa at The Setai in Miami Beach with 7 ocean-view treatment rooms, 5 couples suites, saunas, steam and a cold plunge.

Gold Coast, Queensland

A 90-minute hydrotherapy circuit in Southport with a Finnish rock sauna, 5° ice baths and hot/cold magnesium pools, day pass $49.

Scottsdale, Arizona

Adults-only hotel spa at the Fairmont Scottsdale Princess with a rooftop pool, grotto waterfall pool, sauna, steam room and cold plunge, open daily 6am-7pm.

Charleston, South Carolina

Adults-only luxury day spa in Charleston's Westside offering 42 treatments and a $370 signature package, with reservations required and no walk-in day passes.

Nashville, Tennessee

Upscale day spa in Franklin outside Nashville offering facials, massages, a salt room, infrared sauna and hydrotherapy tub, open daily by reservation.