World's Coolest Hot Springs

The Soak: Healing power on a massive scale—literally, as its real purpose is to supply hot water and electricity to 45,000 Icelanders—this lagoon just outside Reykjavik holds 1.6 million gallons of 99°F–102°F geothermal seawater laced with silica, minerals, and algae.

The Scene: With 400,000 visitors annually, Blue Lagoon has a theme-park feel. Still, a soak here is undeniably cool, like a communal pool party of Icelanders and tourists slathering silky silica mud on their faces and bodies.

When to Go: Year-round, but Iceland’s winters are notoriously glum with just a few hours of daylight, while summers are 24/7 celebrations since the sun barely sets.

The Soak: What’s a little pungent aroma when you’re surrounded by the majesty of some of North America’s most awe-inspiring peaks—including aptly named Sulphur Mountain? Discovered in 1884, these soothing 98°F–104°F waters are loaded not only with sulphate but also with calcium, magnesium, sodium, and bicarbonate.

The Scene: Set amid the glacier-studded panoramas of Banff National Park, the spring-fed pools are serviced by a retro-rustic 1930s bathhouse with splendid views of Mount Rundle. Hike the steep 3.5-mile switchback trail up Sulphur Mountain before a pre-sundown soak.

When to Go: Year-round, but for fewer crowds and peak foliage visit in the morning during early fall.

The Soak: Known as the Sacred Pool, this divine dip in southwestern Turkey lives up to its name: as you float in spring-fed water that’s a relatively refreshing 94°F, look up at a cerulean Aegean sky and down at 2,000-year-old Greek and Roman antiquities scattered on the pool’s floor.

The Scene: The eye candy here is a panorama of gleaming white terraces—Pamukkale means “Cotton Castle” in Turkish—created as flowing water deposited layers of calcium carbonate. Soaking in these natural pools is no longer allowed, but you can snap photos and then visit the nearby Roman city of Hierapolis.

When to Go: Year-round, but early fall is particularly lovely.

The Soak: “No pain, no gain” is the motto at this unique beach just south of the North Island’s Mercury Bay: you have to bring a shovel and dig your own “hot tub,” which for two hours before and after low tide will fill with spring-fed water laced with calcium, magnesium, potassium, silica, and fluorine. Note: also bring a bucket to add cold seawater to regulate the temperature, which can emerge at a scalding 147°F.

The Scene: It’s a communal Kiwi beach bash, so arrive early to stake out your circle of sand.

When to Go: Year-round, but summer (December to March) is ideal.

The Soak: The adults-only Rock Lake, fed by sulfur-tinged springs, reaches a toasty 106°F, but the truly hot ticket is the blazing aurora borealis (northern lights), neon-hued curtains of charged particles that dance across the late-night sky above you.

The Scene: Rock Lake is part of the 105-year-old Chena Hot Springs Resort; located 60 miles from Fairbanks, it has 80 rooms and suites, plus an indoor springs-fed pool (chlorinated and 94°F), a spa, an ice museum, and dogsled tours.

When to Go: Year-round, but the northern lights are most spectacular from September to March.

The Soak: The old adage “monkey see, monkey do” is apropos, as this mountain region’s Japanese macaques (a.k.a. snow monkeys) have taken such a liking to the steamy onsens (Japanese for “hot springs”) that they’ve claimed the best for themselves. All we hapless humans can do is watch—and then head to Yamanouchi town, where a dozen-plus traditional (no swimsuits) communal onsens await.

The Scene: Jigokudani means “Hell’s Valley,” and it is a trek to get to these secluded pools located at 2,790 feet and a mile-plus by foot through formidable forest. But persevering monkey fans will be rewarded.

When to Go: Winter, when the simian-filled springs are steamiest and skiers can hit the slopes at nearby 1998 Nagano Olympics site Shiga Kogen.

The Soak: Enjoy a splash of history at Britain’s only natural thermal springs—the water is believed to have fallen as rain 10,000 years ago—which have vanquished stress for everyone from conquering Celts and Romans (their ancient baths are now a museum) to politicians and poets. Although the water surfaces at a red-hot 113°F, the spa’s intimate Cross Bath and rooftop New Royal Bath are a comfy 93°F.

The Scene: Paging Mr. Darcy! One of Britain’s loveliest Georgian cities, Bath is best known for its honey-hued limestone crescents and celebrated resident-author Jane Austen.

When to Go: Year-round.

The Soak: There’s lots more than hot water on tap at this onetime hippie hangout in Napa Valley: Calistoga’s mud baths are as free-flowing as Merlot. Chill-out types will find an array of spas—from frayed-at-the-edges to five-star—offering 80°F–102°F geothermal pools and volcanic ash mud pits where sassy slathering is not verboten.

The Scene: Founded in 1885, Calistoga’s wines are known to loosen inhibitions and lips—as they did when Samuel Brannan christened it “the Calistoga of Sarafornia” (he meant to say the Saratoga of California).

When to Go: Year-round.

The Soak: Yee-haw! This impeccably restored ghost town, located at 8,600 feet in the San Juan Mountains near Telluride, offers six ways to soak in waters ranging from 85°F–106°F and rich in calcium-bicarbonate, iron, and manganese with a pinch of lithium. The most authentic (and hottest) is under the stars at the source; the most private is the king-bedded Well House cabin for two.

The Scene: Twelve hand-hewn cabins, built by gold miners in the 1800s and given a five-star facelift, bunk up to 42 people. Social hubs are the Saloon (serving organic local cuisine) and the Bath House (with two geothermal pools).

When to Go: Year-round.

The Soak: The high desert—and at 11,482 feet, we mean high—of this geyser-spiked South American region provides a dramatic backdrop for eight secluded pools named for the term “hot water” in the indigenous Kunza language. While not especially scorching at 91°F, they do, however, have a brilliant blue-green color and an ultrarelaxing aura.

The Scene: Maintained by luxury adventure resort Explora Atacama, the pools, north of San Pedro de Atacama, are open to the public but are rarely crowded.

When to Go: Year-round, but the weather is best from October to June.