By the time the scalding waters have trickled down algae-covered travertine to settle in the pools near Bridgeport in the Eastern Sierras, they’re a pleasant 42 degrees or so. They have the kind of mud that day-spas pay a fortune for – and even better views, of the snow-capped Sawtooth Mountains. 

Grab a tub of silica-rich geothermal mud to slather over your face and slip into the hot, mineral waters of Iceland’s famous Blue Lagoon. This otherworldly, milky-blue pool in a lava field outside of Reykjavík is actually manmade: the water is recycled from the nearby Svartsengi geothermal power plant.

Rimmed by a rust-red border caused by deposits of arsenic and antimony sulphides, Champagne Pool gets its name from its effervescent nature. Thanks to carbon dioxide, the pool fizzes and froths like champagne; as tempting as it would be to bathe in a giant glass of bubbles, it’s a bit too hot at 74 degrees Celsius. 

In southern Tuscany, travertine (limestone deposited by mineral springs) pools fed by deliciously warm sulphurous spring water formed over centuries. The water’s power is well-known – said to alleviate ailments ranging from skin conditions to liver issues – and the pools have been frequented since ancient times, first by Etruscans and then by Romans. 

Deep in the Elsey National Park in Katherine, Mataranka Thermal Pool maintains a constant 34 degrees as well as a vivid turquoise colour from its limestone foundations. It’s surrounded by palm-shaded walking trails and the Roper River and nearby is Bitter Springs, another thermal pool that’s deeper and less frequented.

The second-largest geothermal lake in the world (the largest is New Zealand’s Frying Pan Lake – it’s not possible to bathe there due to the high temperature), Lake Hévíz is replenished every 85 hours by mineral-rich waters originating from a kilometre below ground, a subterranean source that, millions of years ago, was the Pannonian Sea.

The Romans were big on bathing but in Bagno Vignoni, it’s thought the popularity of the hot springs predates even them. The Etruscans were fans of the curative waters at Bagno Vignoni, where the whole main square is actually a 49- by 29-metre hot spring    

The Japanese, as they are wont to do, have elevated bathing in hot, odorous water to a high art (complete with strict etiquette). Tamagoyu ryokan, a traditional hot-spring inn, is perched halfway up the active stratovolcano Mount Azuma in Fukushima. Visit in winter for views of snow-covered woodlands from the open-air pool.  

Maintaining a comfortable 42 degrees, the 17 pools that make up Termas Geométricas just outside of Coñaripe are a boon to anyone who’s overdone trekking, climbing and cycling in the Villaricca National Park. Connected by a maze of red walkways, the slate pools are fed by the area’s natural hot springs. 

Close enough for a day-trip from Tokyo, the Hakone spa region is one of Japan’s premier onsen resorts. Gôra Kadan is a ryokan in the grounds of the former summer villa of a member of the Imperial Family. Its spa is fed from a natural spring nearby.  

Known as Baños de Bispo in honour of the bishop who built them for pilgrims seeking healing, these pools are in one of Europe’s prime geothermal spots. The water is said to help treat acne and arthritis – Ourense, a stop along the Camino de Santiago pilgrim route, has been popular for its springs since Roman times. 

This volcanic island was formed by a series of eruptions between 197BCE and 47CE and its name means “Old Burnt Island” – fitting, no? It’s uninhabited but there are several structures, including a church and a bar, so visitors enjoying its hot spring have all their needs covered.

Three natural pools alongside the fast-flowing Lussuer River outside Whiteswan Lake Provincial Park make up Lussier Hot Springs. They’re free and the waters grow colder according to proximity to the river.

In the Kosciusko National Park in the Snowy Mountains, Yarrangobilly Caves Thermal Pool is a fun way to end a visit to the caves. The pool is about 27 degrees year-round but wintertime bathing can be a little chilly, especially when you factor in a dash up the steep steps to the change-rooms in your swimmers!

In the Piazza La Bollente, a steaming fountain supplies bromine- and iodine-rich thermal water to locals, who fill vessels from the central fountain, called La Bollente (“the boiling source”). There are two spas in town where guests can take the waters: the Grand Hotel Nuove Terme and Lago Delle Sorgenti Spa.

Two hours either side of low tide, visitors flock to Hot Water Beach, spades in hand, to dig their own personal spa baths. The geothermal water that bubbles up beneath the sand is hot – up to 64 degrees – and at all other times of the day is covered by the surf. 

If the name of this English city didn’t tip you off, the Roman Baths museum should make its drawcard clear as water. Bath is a spa town par excellence, as evidenced by its Roman bathing complex. Experience those same waters at Thermae Bath Spa where the rooftop pool boasts views of Bath Abbey through the steam. 

Bathe in ancient – like, two million years old – waters that bubble up at a rate of nine litres per second from the Great Artesian Basin at Lightning Ridge Bore Baths. The pool opened in 1962 and the water, which is naturally heated to a steamy 41.5 degrees Celsius, is said to soothe aching muscles.  

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