Spas with upscale

Sopot, Pomerania

A medical resort spa in Sopot built around local brine and mud treatments, open to hotel guests by reservation rather than day visitors.

Auckland

Hotel day spa at Pullman Auckland CBD with a 25m heated pool, sauna, steam room, jacuzzi and gym plus massage and facial treatments.

Vail, Colorado

Hotel spa at the Westin Riverfront in Avon near Vail, with 14 treatment rooms, a saline lap pool, three infinity hot tubs and day passes for non-guests.

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.

Chamonix, Auvergne-Rhône-Alpes

Hotel spa at Heliopic Chamonix with an ice cave, cold-water well, hammams, sauna and a 15m pool facing the Mont Blanc massif, open to day visitors who book a

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

Aix-les-Bains, Auvergne-Rhône-Alpes

An upscale day spa inside Hotel Le Riviera in Aix-les-Bains, with pools, saunas, a hammam and eight treatment rooms open to walk-ins.

Napa Valley, California

Adults-only resort spa built into a wine cave in Napa, with a vineyard-view pool, sauna, steam room and hot tub; reservations required.

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.

Dubrovnik, Dubrovnik-Neretva

Hotel spa near Lapad Bay in Dubrovnik with a salt room, Finnish and infra saunas, a relaxation lounge, and a nine-treatment menu open daily.

Austin, Texas

A fifth-floor hotel spa inside JW Marriott Austin with eight treatments, a heated rooftop pool and a 16-plus minimum age.

San Diego, California

Adults-only hotel spa at Kona Kai Resort on Shelter Island with six treatment rooms, a couples' suite and day-pass access for non-guests.

Jackson Hole, Wyoming

Resort spa at Teton Village with pools, soaking tubs, a rooftop hot tub, and facials built for Jackson Hole's dry alpine air.

Kissimmee, Florida

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

Quebec City, Quebec

A riverside Nordic spa in Old Quebec with an infinity pool, salt-water floating bath and thermal baths along the St. Lawrence, open daily 9am-10pm.

Palm Springs, California

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

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.

Miami, Florida

A 12,000-square-foot hotel spa at Coral Gables' Biltmore, with eucalyptus steam rooms, Himalayan salt saunas and a couples suite; adults-only, reservation

Ocala, Florida

A hotel spa inside Ocala's AAA Four Diamond Equestrian Hotel, offering couples treatments alongside a fitness center and zero-entry pool.

Miami, Florida

AVEDA hotel spa at The Palms in Mid-Beach Miami, offering Ayurvedic-inspired massages, facials and salon services with pool and beach access included.

Calistoga, California

Hotel spa in downtown Healdsburg with a garden patio, jacuzzi and pool access, open daily 9am-5pm for guests and day visitors.

Chicago, Illinois

A hotel spa inside Four Seasons Chicago, Streeterville, with an indoor infinity-edge pool, whirlpool and fitness centre, open on a day-pass basis.

Scottsdale, Arizona

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