Spas with moderate

Sierraville, California

A non-profit hot springs retreat near Lake Tahoe with natural spring pools, reservation-only day and evening soaks, camping and rooms, closed Mondays and

Philadelphia, Pennsylvania

A Russian-Turkish bathhouse in Southampton, outside Philadelphia, with platza massage, a pool and multiple heat rooms, open to walk-ins with day passes.

San Diego, California

Adults-only day spa at Mission Bay Resort with massage, facials, Himalayan salt treatments and couples suites; walk-ins and day passes welcome.

Austin, Texas

A day spa and med spa in North Burnet offering massage, facials, and injectables, with walk-ins and day passes accepted.

Naples, Florida

A 4,500-square-foot beachfront spa at LaPlaya Resort in North Naples offering massages, facials and nail services, open daily 9am-5pm.

Tucson, Arizona

Adults-only hotel spa at El Conquistador Tucson with a salt therapy lounge, heated outdoor pool and mountain views, day passes available to hotel guests.

Palm Beach, Florida

A Palm Beach Gardens studio offering 60-minute private-suite sessions combining infrared sauna, cold plunge and vitamin-c shower.

Mendocino, California

A redwood hot tub and sauna spa in Mendocino village, offering massage and private soaks mainly for guests of the adjoining Sweetwater Inn.

Sárvár, Vas

Large thermal bath complex in Sárvár with indoor and outdoor pools, a sauna world, slides for kids, and medical spa treatments.

Sárvár, Vas

A large thermal and wellness complex in Sárvár with indoor and outdoor medicinal pools, slides, a sauna world, fitness center and massage treatments.

Bad Wörishofen, Bavaria

Adults-only thermal baths in Bad Wörishofen with palm-house pools, mineral pools and saunas; day passes available, minimum age 16.

Puyehue, Los Lagos

A hot-springs resort inside Puyehue National Park with two mineral pools, cabins, river-side domes, camping, and day passes for non-guests.

Chaves, Norte

Thermal baths complex in Chaves, Portugal, built around natural hot springs, with hydrotherapy, sauna, steam room and massage on a day-pass basis.

Merano, Trentino-South Tyrol

Central thermal bath complex in Merano with 25 pools, a sauna world, thermal park and medical spa area, open daily year-round with walk-in day passes.

Portorož, Coastal-Karst

Thermal baths and seawater pools in Portorož, open daily 7am–9pm with walk-in day passes and a large sauna park.

Queenstown, Otago

Adults-only bathhouse in central Queenstown with heated, ambient and cold pools, sauna and steam room, day pass $99.

Boston, Massachusetts

A Norwood, Massachusetts day spa built around a hot-cold hydrotherapy circuit of mineral baths, saunas, steam and cold plunges, open daily with a day pass.

Jackson Hole, Wyoming

Hotel spa inside the Rusty Parrot Lodge in downtown Jackson Hole offering massage, facials and couples treatments with hot tub access, day passes welcome.

Portland, Oregon

An 18-and-up, clothing-optional spa in Portland's Kerns neighborhood with a salt hot tub, sauna, steam room and cold plunge, reservation required.

Seattle, Washington

A quiet, clothing-optional day spa in Greenwood with soaking pools, saunas and a steam room, women-owned and open to all genders on Wednesdays.

Miami, Florida

A walk-in sauna and cold plunge studio in Miami built around contrast therapy, with day passes and split morning and evening hours.

Denver, Colorado

A 6,000-square-foot hotel spa in downtown Denver's Granite Tower, open to day-pass visitors 18 and older for $40 to $75.

New York City, New York

Korean jjimjilbang-style spa in Manhattan with saunas, steam room, soaking tub and body scrubs, open daily 8am-11:30pm on a day-pass basis.

Denver, Colorado

A hotel spa in downtown Denver with a $150 day pass covering pool, steam room, whirlpool and fitness centre access, open to non-guests.