Spas with upscale

Dead Sea, Balqa

Resort spa on the Dead Sea shore with 40 treatments, thermal pools, sauna and steam, open to day guests aged 16 and up.

Aspen, Colorado

O2 Aspen is a day spa on South Mill Street offering facials, a yoga studio and a retail boutique, open daily with walk-ins welcome.

Berkshires, Massachusetts

A lakeside resort in Egremont with a seasonal pool and sauna for overnight guests only; no day passes and no spa treatments on offer.

New York City, New York

Adults-only day spa on Governors Island with heated outdoor pools, saunas and an Italian-style café, reachable by ferry from Manhattan.

Bangkok

Hotel spa at SO/ Bangkok on Sathorn Road offering facial, body and beauty treatments plus rooftop infinity pool and fitness access, hotel guests only.

Shibu Onsen, Nagano

A ryokan in Shibu Onsen with indoor and outdoor hot-spring baths fed by two blended mineral springs, open only to overnight guests.

Scottsdale, Arizona

A hotel spa at Scottsdale Camelback Resort, open only to resort guests staying in the property's villas at the base of Camelback Mountain.

Scottsdale, Arizona

An adults-only hotel spa in Old Town Scottsdale with sauna, steam room, cold plunge and thermal pools, open to hotel guests 21 and up.

Goa

A hotel spa inside Sea Queen Beach Resort on Colva Beach, Betalbatim, Goa, open to overnight guests with one signature treatment called The Sea View.

Tyrol, Bavaria

Hotel spa in Kreuth-Reitrain near Tegernsee with a 3,000 sqm onsen-style bathing area, hot and cold pools, saltwater pools and sauna, open on a day-pass basis.

Punta Cana, La Altagracia

Adults-only all-inclusive resort spa in Bávaro with a gym, sauna and couples treatment rooms, open to hotel guests aged 18 and up.

Pagosa Springs, Colorado

A mobile container-trailer spa in Pagosa Springs offering infrared sauna and cold plunge contrast therapy, adults only, by reservation.

Dallas, Texas

Hotel spa inside The Highland Dallas in Lower Greenville, Dallas, with a sauna, steam room, outdoor pool and couples treatment rooms.

Carlsbad, California

Adults-only hotel spa in Carlsbad with steam room, separate men's and women's lounges, and couples massage as its signature treatment.

Lake Tahoe, California

Hotel-only spa at a lakefront resort in South Lake Tahoe, with an outdoor heated pool, Jacuzzi and treatment rooms aimed at couples.

Tiberias, Northern District

Adults-only boutique hotel spa on the Sea of Galilee in Tiberias, set in a former hospital building, with a seasonal pool and couples' treatments.

Scottsdale, Arizona

Hotel spa at The Scott Resort offering massages, facials and restorative treatments for guests amid palm-lined grounds in South Scottsdale.

Las Vegas, Nevada

A 17,000-square-foot hotel spa in Las Vegas with 15 treatment rooms, a fitness center and a yoga studio, open to Palms guests daily.

Napa Valley, California

Adults-only resort spa in Napa Valley with pools, sauna, steam and a fitness center, open to hotel guests and club members via day pass.

Edinburgh, Scotland

Hotel spa inside The Caledonian on Princes Street with a thermal pool, sauna, steam room and relaxation lounge, open daily 6am to 9pm.

Las Vegas, Nevada

Hotel spa at Virgin Hotels Las Vegas with massages, skin treatments, a Roman-style bathhouse, relaxation lounge and thermal pool, open to hotel guests.

Tucson, Arizona

A hotel spa at an 80-acre Sonoran Desert resort in Tucson, open to overnight guests, with three pools, hot tubs, sauna and yoga classes.

Sedona, Arizona

Hotel spa at Hilton Sedona Resort at Bell Rock offering day passes with a relaxation lounge, steam room, sauna and thermal pool, open daily 6am-8pm.

Buxton, England

A hotel spa built into Buxton's historic Crescent, centred on a thermal pool, hydrotherapy circuit and salt room, open to hotel guests only.