Spas with groups

Thermopolis, Wyoming

Free public bathhouse in Thermopolis, Wyoming, with indoor and outdoor mineral soaking pools held at 104°F, open seven days a week.

Palm Springs, California

A 10-room mineral hot springs hotel in Desert Hot Springs near Palm Springs, offering day passes to its 120°F spring-fed pools, sauna and massage rooms.

Karjalohja, Uusimaa

Lakeside resort spa on Lohjanjärvi in Karjalohja, about an hour from Helsinki, with a day pass, thermal pool, salt room and restaurant.

Park City, Utah

A sauna-and-cold-plunge day spa in Park City with memberships, private group buyouts, and reservation-only access.

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.

Los Angeles, California

A wellness retreat in Westlake's Wilshire corridor offering cold plunge, sauna and movement classes, built around group and community sessions.

Carmel-by-the-Sea, California

A hotel spa inside Carmel-by-the-Sea's Hyatt Regency Monterey property, with hydrotherapy, sauna and a relaxation lounge for guests and couples.

Naples, Florida

A hotel spa inside the Inn on Fifth in downtown Naples, open daily for massages, facials, nail services, sauna, steam room and lounge access.

Arima Onsen, Hyogo

Hotel spa in Arima Onsen with Arima's rare iron-rich "ginsen" waters, outdoor baths, sauna and jacuzzi, run as an all-inclusive overnight stay.

Prague

A beer-spa and wellness venue in Prague's Nové Město district offering beer-bath tubs, massages, and a saunarium, open daily from 11am to 11pm.

Miami, Florida

A hotel spa at Eden Roc Miami Beach in Mid-Beach with sauna, steam room, cold plunge and thermal circuits, open to resort guests only.

Spa, Liège

Hotel spa in the town of Spa, Belgium, with a thermal pool, relaxation lounge and restaurant, open to day-pass visitors, not just hotel guests.

Catskills, New York

A Catskills retreat center with a Tibetan-style spa offering sauna, steam, pools and cold plunge, built around overnight stays and group programs.

Miami, Florida

Hotel spa at the Fontainebleau Miami Beach resort on Collins Ave, open to hotel guests only.

Miami, Florida

A hotel spa inside the Four Seasons in Brickell, reserved for hotel guests, with rooftop pool and bay views as part of the stay.

Pai, Mae Hong Son

Affordable day spa near Pai's Wednesday Market open daily except Monday from 3pm to 9pm, with walk-in access and a sauna.

Tulum, Quintana Roo

Beachfront resort in Tulum pairing overnight stays with spa treatments, yoga and fitness classes, open to hotel guests only.

Philadelphia, Pennsylvania

A private-reservation spa in Philadelphia's Manayunk neighborhood for date nights, birthday and bachelorette parties, with hot tub, sauna and massage chairs