Spas with reservation required

Chianciano Terme, Tuscany

Thermal day spa in Chianciano Terme offering day passes, couples massages and a wellness-food menu, closed Thursdays and Wednesdays.

London, England

A Russian-style banya bathhouse in Belgravia offering oak-lined steam rooms, cold plunge pools and leaf-massage rituals, with day passes by reservation only.

Port Douglas, Queensland

Ayurvedic-style massage and bathhouse studio in Port Douglas offering couples treatments, yoga and reformer Pilates, bookings required with no walk-ins.

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.

Chicago, Illinois

Luxury hotel spa in River North, Chicago, with an indoor pool, steam room and lounges, open to both hotel guests and outside bookings by reservation.

Marana, Arizona

Adults-only hotel spa at Dove Mountain Resort in Marana with desert-themed treatments, an infinity-edge pool, sauna and steam room; facility access comes with

Lake Tahoe, California

A 17-room, adults-only hotel spa at Lake Tahoe's Ritz-Carlton with a heated lap pool, sauna and steam room; day pass access requires booking a treatment.

Scottsdale, Arizona

Resort spa at Camelback Inn in Scottsdale with 20 treatment rooms, a thermal circuit and day-pass access open to non-guests.

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.

New York City, New York

A 30-treatment luxury hotel spa in Lower Manhattan with a lap pool, steam rooms and the German GREEN PEEL facial as its signature service.

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.

Jackson Hole, Wyoming

A hotel spa at Four Seasons Jackson Hole with treatment suites, whirlpools, a cold tub, salon services and fitness facilities, reservation-only.

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.

Santa Fe, New Mexico

Small hotel spa at Hotel Loretto in downtown Santa Fe offering two seasonal treatments by reservation, no walk-in day pass.

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.

San Diego, California

Resort spa on Mission Bay offering massages, facials and body treatments, with walk-ins welcome and a gym and yoga classes on-site.

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

Miami, Florida

Hotel spa at The Ritz-Carlton Key Biscayne, Miami, with treatment suites, sauna, steam room and whirlpool, open to hotel guests 18 and up 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.

Santa Fe, New Mexico

Small hotel day spa in downtown Santa Fe with a soaking pool, five treatment rooms and 25 services, open daily 8am-5pm by reservation.

Miami, Florida

Hotel spa inside Trump National Doral with 42 treatments, couples massages, sauna, steam room, cold plunge and jacuzzi, open daily 9am-7pm.