Spas with reservation required

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.

Santa Fe, New Mexico

A 16,000-square-foot adults-only hotel spa at Hilton Buffalo Thunder near Santa Fe, with separate men's and women's saunas, steam rooms and whirlpools.

Nashville, Tennessee

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

Soufrière

Hotel spa at Ladera on the Pitons ridge in Soufrière, with day passes, couples treatments and volcanic mineral pool access.

Minneapolis, Minnesota

A St. Paul wellness studio in Macalester-Groveland offering infrared sauna, float tanks, salt therapy and cold plunge by reservation, adults-only, day-pass

Carefree, Arizona

A 20-plus-acre desert wellness resort in Carefree, Arizona, with a full spa, pools, and 100-plus weekly fitness and mindfulness classes open to day visitors by

San Diego, California

A La Jolla medical spa specializing in lymphatic drainage, colon hydrotherapy and detox treatments, open since 1993, adults only, by reservation.

Chicago, Illinois

Upscale day spa in Lincoln Park, Chicago, where booking any treatment unlocks all-day access to a hydrotherapy circuit, thermal suite and outdoor terrace.

Philadelphia, Pennsylvania

Hotel spa on the third floor of The Rittenhouse overlooking Rittenhouse Square, with massage, facials, body treatments and a salon.

Palm Springs, California

Downtown Palm Springs day spa built around a natural hot mineral spring, with private mineral baths, sauna, steam room and massage.

Asheville, North Carolina

A day spa in a converted barn on Horse Shoe Farm near Asheville, offering massage and body treatments amid farm and mountain surroundings.

Hudson Valley, New York

Hotel spa inside The Abbey Inn in Peekskill, overlooking the Hudson River, with six treatments including a Japanese head-and-foot package.

New York City, New York

Thermal bath circuit and massages in a restored 1883 Tribeca textile factory, with a skylit tepidarium and candlelit thermal pools; reservation required.

Rishikesh, Uttarakhand

An upscale riverside resort 18 km outside Rishikesh with an in-house spa, yoga studio and restaurant, open only to overnight guests by reservation.

Asheville, North Carolina

Ayurvedic destination retreat in the Blue Ridge Mountains near Asheville, with day-pass spa visits and multi-night panchakarma cleanses by reservation.

Key West, Florida

A hotel spa at Pier House Resort in Key West for guests only, offering couples treatments for ages 14 and up with advance reservations.

Philadelphia, Pennsylvania

A reservation-only hotel spa inside W Philadelphia's Ritz-Carlton Residences in Center City West, open daily with a day-pass option.

Los Angeles, California

A hotel spa at the Conrad Los Angeles in Downtown LA, open only to hotel guests by reservation, with an adults-only, couples-friendly setting.

Byron Bay, New South Wales

Hotel day spa at Crystalbrook Byron offering customizable massages and facials, open daily with Sunday by appointment only.

Montecatini Terme, Tuscany

Adults-only hotel spa in Montecatini Terme built around a four-elements wellness philosophy, open daily 11:00-19:00 with day passes by reservation.

San Francisco, California

A Japantown bathhouse open for 50+ years, with a Japanese-style thermal pool and relaxation lounge, reservation required, adults only.

Austin, Texas

Adults-only resort spa on Lake Austin offering all-inclusive overnight stays and limited day passes to pools, saunas, steam rooms and lake activities.

Hudson Valley, New York

A French-inspired hotel spa in the center of Rhinebeck village, open to overnight guests by reservation.

Bordeaux, Nouvelle-Aquitaine

Hotel spa at Palais Gallien in Bordeaux offering Nuxe skincare treatments built around the brand's signature Huile Prodigieuse, open daily by reservation.