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Iceland's Blue Lagoon is one of the picturesque places in the world to have a soak.

In the world of spa treatments, it all goes back to water-and travel. After all, the word "spa" itself comes from Spa, Belgium, a popular watering spot back in the 1600s. In the centuries since, cultures all over the globe turned to natural, mineral-rich waters to treat a wide array of concerns, from the medical (sinus issues, muscle and joint pain) to cosmetic (skin clarity, psoriasis). The ancient Romans turned soaking into an art form-and a part of daily life-and as the Roman Empire grew, baths known as thermae were established wherever mineral springs were discovered. Over the years, many of these ancient hot spring towns grew into wellness resorts, particularly once European doctors started recommending "water cures" in the 18th century. With so many steamy spots to choose from in the world, we've narrowed our list down to natural hot, mineral, and geothermal springs in historic, picturesque locations, including two right here in the U.S. Here are some of the prettiest places to jump in and say "ahhh."

SEE THE HOT SPRINGS!

Banff Upper Hot Springs, Banff National Park, Alberta, Canada

Surrounded by dramatic alpine views, these hot springs in western Canada were considered a sacred healing site by the area's native residents. In 1882, workers building the Canadian Pacific Railway happened upon two of the spring pools at the base of Sulphur Mountain-and the news quickly spread. The first European visitors arrived in 1884, and two years later construction on a bathhouse begun. The Banff Upper Hot Springs bathhouse, completed in the mid-1930s, has been declared a protected Heritage Building.

The Benefits: Located at 5,200 feet above sea level, Canada's highest natural springs are rich in key minerals like sodium, magnesium, bicarbonate, calcium and sulfate, which have skin healing and muscle-relaxing properties. Despite their long journey from the center of the earth, these waters are also the hottest in the Rocky Mountain range, clocking in at up to a muscle-warming 104 degrees.

How to Soak: The Banff Upper Hot Springs complex-which includes one large pool and a bathhouse-is located about a mile and a half south of the town center, and is accessible by public Banff Roam Bus service; buses run every 40 minutes. The pool is fed by water directly from the spring source, which lies in a protected part of the National Park. www.hotsprings.ca, $7.30 entrance fee.

Ma'In Hot Springs, Jordan

A spa with biblical roots.

Like those of their neighbor, the Dead Sea, the healing powers of these desert oasis springs are biblical: King Herod would travel here often for medical treatment and legend has it that Salome did her famous dance in his nearby villa. Since then, kings, queens, and commoners of all types have come to enjoy the hot and cold springs, many of which tumble down from picturesque waterfalls.

The Benefits: Known locally as Hammamat Ma'in, the springs originate from winter rainfalls in Jordan's highland plains. As the water makes its way through the Wadi Zarqa Ma'in valley, underground lava fissures help heat them (temps range from 104 to 145 degrees) and infuse them with skin-healing minerals like hydrogen sulfide, potassium, magnesium, and calcium. Stand under one of the hyperthermal waterfalls for a natural deep-tissue massage.

How to Soak: The springs are located in a desert valley near the Dead Sea, about 866 feet below sea level; it's around a 20-minute drive from the town of Madaba and one hour from capital city Amman. The public bathing complex at Hammamat Ma'in includes Roman baths at the base of a waterfall (visitjordan.com; $14 entrance fee). The facility is popular with local families and can get crowded on weekends.  For a more private experience, check-in to the Evason Ma'In Hot Springs resort next door, where guests enjoy after-hours entry to the main springs, as well as access to falls and pools located on the hotel grounds. (011-962-5-324-5500; sixsenses.com/Evason-Ma-In; from $207 per night).

San Miguel de Allende, Mexico

Discover balnearios popular with emperors-and movie stars.

Modern-day Mexico is home to hundreds of mineral spring sites, and it's said that the tradition of soaking in these balnearios can be traced far back as the Aztecs (16th-century emperor Montezuma was a fan). Today, some of the most popular, and prettiest, sites lay just outside San Miguel de Allende in central Mexico. Though native peoples were surely making use of these thermal waters for centuries, it wasn't until the town's "re-discovery" by artists and Mexican movie stars in the 1950s that formal spas and baths were constructed.

The Benefits: The area around San Miguel de Allende features thermal, alkaline, sulfur and fresh water springs, though the first two are most popular for bathing. Despite legends that these waters have "age-reversing" effects, most bathers come to relax under the heated falls and soak up the generally therapeutic natural minerals.

How to Soak: There are several mineral springs along the road from San Miguel de Allende to Dolores Hidalgo that are open to the public for a fee. Escondido Place is a favorite and has five open-air thermal pools, three covered springs, and lush grounds perfect for picnics. escondidoplace.com; $7.50 entrance fee.

Blue Lagoon, Iceland

The scenery, and the effects, are otherworldly.

A heating company formed the lagoon (which holds 1.5 million gallons of sea- and freshwater) to explore geothermal heating methods in the late 1970s. By 1981, people were bathing in the lagoon-and noticing marked improvements in skin conditions. The site became a popular tourist attraction, with official public facilities opening in 1987 and a full spa in 1999.

The Benefits: With its volcanic rocks, electric green moss, and steaming waters, the area around the Blue Lagoon looks like something from another planet. Fans of the waters agree that the results are otherworldly. High amounts of silica help exfoliate skin, strengthen its barrier function, and heal inflammation, while minerals from the seawater revitalize skin. Microorganisms found here also help reduce signs of UV damage and stimulate collagen production. Skin care products made with the therapeutic waters make great souvenirs.

How to Soak: The facility, 40 minutes from the center of Reykjavik, includes steam baths, sauna, relaxation areas, and lagoon pools. Enjoy the massaging waterfalls and lather on some pure geothermal silica mud (provided free of charge). In-water massages and other spa treatments are available for an additional fee. bluelagoon.com; $39 entrance fee.

Budapest, Hungary

Drinking the water is as healing as soaking in it.

Ancient Celtic settlers were the first to make use of the therapeutic waters (they named the area Ak-Ink, or "ample water"), followed by the Romans, who built the first official baths and re-dubbed the place Aquincum. Though the bathing culture continued through centuries of Hungarian and Turkish rule, the traditions floundered in the 18th century-until the re-discovery of some thermal springs in the 1800s. A scientific interest in the benefits led to the construction of some of the city's most famous bathhouses, some which remain today.

The Benefits: The thermal waters are rich in a variety of minerals, including fluoride, calcium, hydro-carbonate, sodium, magnesium, sulphate, and metabolic acid. The combination has proved effective in treating chronic arthritis and other joint illnesses and orthopedic issues. The water from drinking wells is also high in similar minerals, and is good for treating gastric ulcers and various internal inflammations.

How to Soak: There are enough mineral springs under the city of Budapest to feed more than 50 public baths and pools, numerous private spas, and countless drinking fountains. We suggest the stunning Szechenyi Bath, which opened in 1913. The complex includes three large outdoor pools, heated to varying degrees, plus several pools with jets and waterfalls, saunas, and spots for aqua-aerobics and other therapies. szechenyibath.com; entrance fee from $12.50

Bath, England

Take the cure among Roman ruins.

Archeological evidence suggests activity around these springs in southwest England as far back as 8,000 B.C. Those water-crazy Romans constructed the first formal baths in the first century AD (visitors can tour the remains today) and the baths' popularity didn't wane in the centuries that followed. As Jane Austen fans know, the waters were popular throughout the 1700s and 1800s with travelers looking to "take the waters." In 2006, after more than a decade of renovations, the Thermae Bath Spa complex opened in some of the most historic bath sites.

The Benefits: The three wellheads under the center of Bath are sourced by ancient rainwater that has made its way up through the region's limestone faults. The waters (which can be as warm as 117 degrees) contain more than 42 minerals, including sulphate, calcium, silica, iron, and chloride. Doctors have sent patients here for centuries to treat rheumatism, psoriasis, gout, and even infertility; injured WWII servicemen also came here for rehab. These days, most soakers seek relaxation and relief from skin issues.

How to Soak: The Thermae Bath Complex is right in the center of Bath, about a 15-minute walk from the railway station. The main building houses the largest of the thermal baths, the New Royal Bath, has a whirlpool as well as a "lazy river," a heated rooftop pool, aromatherapy steam rooms, and a full-service spa (thermaebathspa.com; entrance fees from $34). Across the street, the smaller (and very basic) thermal Cross Bath stands at the site where ancient Celts and Romans honored their respective goddesses (thermaebathspa.com; $21 for 90 minutes).

Arenal Hot Springs, Costa Rica

Where the volcano views are as stunning as the waters are relaxing.

Costa Rica is home to six active volcanoes and 61 more that are dormant or extinct. Thanks to all this geothermal activity, the country also boasts several hot springs sites, most notably around the Arenal Volcano in the northwest. Technically still active (it's said to be "resting"), Arenal's heat and minerals infuse streams that flow through the marshes and grasslands at its base. Several hotels offer access to the springs, but the original-and the gold standard-is the Tabacón Grand Spa Thermal Resort, opened in 1993.

The Benefits: Tabacón's hot springs are 97 percent rainwater that has sunk to the earth's core and been heated, and the remaining three percent is magma-based. As the mixture rises back to the surface, it brings with it the minerals imbedded in the earth. The springs are naturally heated to a muscle-relaxing 77 to 122 degrees and the high levels of hydrothermal flora and fauna strengthen the skin's defense system and repair surface damage. Even better, the springs are low in sulfur. Meaning you won't stink after taking a dip.

How to Soak: If staying at the luxury resort is not in the budget, buy a day pass to enjoy the dozen mineral pools (including one with thermal water slide and another with a swim-up bar), three thermal waterfalls, and sweeping volcano views. tabacon.com; from $60 for a day pass.

Dunton Hot Springs, Colorado

An old mining town is reborn as a spa haven.

Back in the early 1500s the Ute Indians enjoyed these southwest Colorado hot springs, which sit about 8,600 feet above sea level. Ore miners (and speculators) came to the region in the 1880s, and a private homestead was established on the land that's now Dunton. The owners recognized the hot springs' moneymaking potential and started charging a nickel to take a dip. The first "hot tub" was built in a log-lined pit, followed by various shack bathhouses. By 1918, though, the mining boom was bust and the town deserted. The current owners took over in 994 and spent seven years turning the whole town into an upscale resort.

The Benefits: Controlled by tectonic forces, the naturally heated Dunton springs are high in iron and magnesium, with trace amounts of lithium. Along with the therapeutic benefits of the minerals and heat (temps range from 85 to 106 degrees), soakers get the added bonus of calcium bicarbonate, which helps open peripheral blood vessels and improve circulation.

How to Soak: Dunton's deluxe cabins start at $550, but day passes are available for travelers who aren't spending the night or booked in the spa (treatments are $185). Once on site, you can choose to soak in one of several pools, including the renovated 19th Century bathhouse, two outdoor pools, or directly at the source. duntonhotsprings.com; $115 for a day pass, including lunch.

Saturnia, Italy

Thank the gods for these healing waters.

Legend has it that hilltop Saturnia's thermal springs bubble up at the exact spot where Jupiter's thunderbolt fell in a battle with Saturn. The Bronze Age Etruscans were the first to partake of the waters, and even built a temple on the site to thank the gods for this gift; later, the Romans constructed what some say was the world's first public bathhouse. After getting a bad rep in the more puritanical 14th century (some thought the hot waters marked the gates of Hell), the springs were re-discovered in the 1800s and continue to be the Tuscan town's claim to fame.

The Benefits: The waters originate from Monte Amiata, a dormant volcano that still pumps water from its craters and rivers. Along with a mineral mix including sulfur, bicarbonate, and alkaline, the water contains plankton, known for its ability to calm and strengthen skin. The combination has also proven beneficial for muscle, joint, cardiovascular and respiratory issues.

How to Soak: The stunning Cascate del Mulino, just outside of town, is a series of thermal waterfalls that cascade into natural pools of travertine rock. The water bubbles up at about 99 degrees year-round, making this a popular relaxation spot even in the winter, and at night (access is available 24/7, at your own risk.) There aren't any facilities at the park-just strip down to your bathing suit and hop in. cascate-del-mulino.info; free.

Hot Springs, Arkansas

Taking the waters, Victorian-style.

Evidence suggests that a variety of Native American tribes came together in peace to bathe in these waters in the Ouachita mountain valley. A naturalist and a chemist were sent to the region following the Louisiana Purchase, and sent word in 1804 of steaming waters and natural minerals. By 1828, simple hotel had been built to shelter bathers and over time dozens of thermal spas were opened, with the additional enticement of horse racing and gambling. The casinos aren't as prominent now, but you can still stroll streets lined with Victorian houses and historic hotels.

The Benefits: The town's thermal waters are sourced from 47 springs on the western slopes of Hot Springs Mountain. As they make their way up through the earth, the springs are infused with an array of minerals and heated to about 143 degrees; the combination has proved effective in treating symptoms of arthritis, gout, and joint and rheumatic issues. You are welcome to fill up on cold mineral drinking water at several pumps around town.

How to Soak: There are several hotels and spas in town that make use of the thermal waters, but for a more traditional experience, head into Hot Springs National Park. Get a history lesson at the Fordyce Bathhouse, now a museum. Then get in the waters yourself at the Quapaw Bath. First opened in 1922, the facilities include private mineral baths—the perfect choice for those not excited about soaking with strangers. quapawbaths.com, $30 for a private mineral bath.

Kusatsu, Japan

The mountain town of Kusatsu in central Japan is one of the oldest hot springs sites in the country, with claims of travelers soaking here as early as the 2nd century. Samurai came in the 1600s, looking to heal their wounds. By the 1700s Kusatsu was a booming resort destination for those suffering from red light district illnesses like syphilis. The interest became scientific in 1876 when a German doctor began researching the healing powers of the waters, and helped create more targeted medical treatments using the springs.

The Benefits: Kusatsu's location near one active volcano and two dormant ones means there are more than 100 springs and baths, called onsen. Full of sulfur and healing minerals from the volcanic earth, the waters treat bruises, sprains, stiff muscles, and burns, as well as chronic indigestion. Temperatures can reach a scalding 129 degrees, so bathing is not allowed in the hottest pools.

How to Soak: There are several public bathhouses in Kusatsu, one of the most popular being Sainokawara Rotenburo. This open-air bath in Sainokawara Park can accommodate up to 100 bathers and is open year-round (japan-guide.com; $6 entrance fee). Otakinoyu has outdoor pools and a wooden bathhouse with seven tubs of varying temperatures (japan-guide.com; $10 entrance fee). Located near a source spring, Shirohatanoyu, one of the eighteen free local communal baths, has two small tubs (japan-guide.com; free).

Yambajan, Tibet

Soak in some of the world's most picturesque springs—if you can get there.

Tibet can be a complicated country to get to (see our advice here). Once there, you can visit numerous hot spring sites, with Yambajan easily being the most picturesque. Glaciers, ancient forests, and snow-capped hills surround the town, which sits on a cold plateau at the base of the Nyainqentanglha Mountains. There are eight springs here, all with evocative names like Bread-Steaming Hot Spring (where bread can be cooked over the steam heat), Vinegar Boiling Spring, and Fish-Cooking River (which runs so hot, fish get boiled and float to the surface).

The Benefits: Yambajan is home to several types of thermal waters, including geysers and springs ranging from warm to boiling (the water in the main bathing pools is cooled in open-air cisterns before it is deemed safe for soaking). While the springs are high in sulfur and other minerals thought to be therapeutic, most travelers come to soak up the muscle-relaxing heat and peaceful atmosphere. Note that because of the high-altitude, long soaks and vigorous exercise in the hot waters are not recommended and you should drink plenty of water to stay hydrated.

How to Soak: The safest place for soaking is in one of the indoor and open-air bathing and swimming pools that have been built along the geothermal field. For the best views, come in the early morning, when the steam rising off the pools seems to melt into the snow-capped mountains in the background. Yambajan is accessible via public bus from Lhasa. tibettravel.info; $5 entrance fee.