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Transvulcania, Spain -

Encompassing a distance of 47 mi (76 km) and run in May on La Palma in the Canary Islands, this epic challenge over razor-sharp volcanic rock tests strength and stamina in equal measure. Runners negotiate over 6,561 ft (2,000 m) of ascent, but the real killer is the bone-jarring descent.

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Comrades Marathon, South Africa - The world’s largest ultra-marathon, this 56-mi (90-km) feat of endurance takes place over 12 hours, with five colossal hills to contend with. It takes place in May out of Durban or Pietermaritzburg.

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Endurancelife Coastal Trail Series, England -

Run from October to May, these coastal runs include the South Devon Ultra, a 35-mi (56-km) dash from Beesands village through an Area of Outstanding Natural Beauty.

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Snowdonia Marathon, Wales -

The road surrounding the highest mountain in Wales provides the route for this scenic challenge, which takes place in October. The 26-mi (42-km) undulating route does include some tricky trail running though.

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GODZone Adventure Race, New Zealand - Do you laugh in the face of adversity? Is fear your friend? Then this monster is for you. Set over trail, river, road, and mountain, the "GODZone" is 852 mi (530 km) of unforgiving terrain. Competitors hike, trek, mountain bike, and kayak through a spectacularly diverse environment, the location of which changes annually. GODZone is always run in February.

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Ultra-Trail du Mont-Blanc, France, Italy, Switzerland -

Regarded as one of Europe’s mightiest running challenges, the 105-mi (170-km) Mont-Blanc race takes place in August in a typical Alpine environment—a mixture of rain, snow, and sun. Beginning in Chamonix, the route stretches through three countries and 10 strenuous climbs along the way.

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The Dragon's Back Race, Wales -

It doesn’t get much tougher than this! A daunting 180 mi (290 km) in length, the Dragon’s Back Race is considered one of the most challenging mountain races in the world. There are no defined trails— runners follow the spines of Wales' most famous mountain ranges. The five-day competition is run every two years in June.

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Strongman Run, Netherlands -

One of Europe’s most popular obstacle courses, this 15-mi (24-km) challenge takes place throughout the year at various venues across the continent. If you’re up for tackling hurdles, deep mud pits, dark brooding water holes, ice-filled ponds, and climbing nets, this crazy event is for you! It reaches the Dutch town of Hellendoorn in September.

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The UK Wife Carrying Race, England - Yes, you read right! There is a race run by husbands every March near Dorking. Wives are hoisted over strong shoulders during a 1,246-ft (380-m) dash, some of it uphill. Expect fits of giggles and threats of divorce along the way.

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Spartan Race, Dubai - Guaranteed to haul you out of your comfort zone, this challenging obstacle course sees competitors running through mud and water, climbing hills and mountains, crawling under barbed wire, and jumping fire. Spartan is a worldwide initiative, and several races are organized throughout the year.

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Lavaredo Ultra Trail, Italy -

Run in June, this is a visual treat, set as it is in the beautiful Dolomites. Marked out at a distance of 74 mi (119 km), and with 19,192 ft (5,850 m) of ascent, the trail takes runners near the Tre Cime di Lavaredo (pictured), three awesome peaks that straddle the South Tyrol and Belluno borders.

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Le Marathon du Médoc, France -

Wine, oysters, cheese, steak, and even champagne are among the treats offered up to runners as they commute along the 26-mi (42-km) course, with some opting to run in fancy dress. The fun takes place every September.

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Kilian's Classik, France - Setting off from Font-Romeu in the Pyrenees, runners tackling this picturesque mountain trail race never run below 5,577 ft (1,700 m). In fact, they sometimes touch a giddy 8,467 ft (2,581 m). The race takes place in July.

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Braemar Gathering Hill Race, Scotland - Enter this Highland fell race and you’ll enjoy a royal sendoff—Queen Elizabeth II watches over the start of this annual 3.5-mi (5.6-km) challenge, which is part of the cultural festival program. Held in September and set in the scenic Cairngorms, this is the oldest hill race in the world.

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ÖTILLÖ swimrun, Sweden - This 75-km (46-mi) challenge begins on the island of Sandhamn and includes a 6-mi (10-km) swim in a wetsuit and sodden training shoes. The race takes place in September, when water temperatures begin to dip. The destination is Utö, in the stunning Stockholm Archipelago.

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The Beast, England -

Run in September at Corfe Castle, Dorset. Good for beginners, this 13-mi (21-km) track of trail and grass meanders over plenty of hills, and is fairly tough in places. The 1,000-year-old castle provides a wonderful backdrop. 

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The Gherkin Challenge, England - One of London’s most iconic buildings, the 590-ft (180-m) Gherkin stands as a gleaming, architectural wonder. It’s also the venue for this brutal tower run, where the insanely fit leap up almost vertical staircases to the 38th floor, the idea being to leave behind 1,037 steps in the shortest time. It destroys legs every September.

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Cayman Islands Marathon, Cayman Islands - Held in December, this is one of Grand Cayman's biggest annual events. The 26-mi (42-km) two-loop course begins in the capital, George Town, and is, for the most part, foot-friendly flat.

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New York City Marathon, USA - This is the biggest marathon in the world, with the 26-mi (42-km) course taking in the five boroughs of Staten Island, The Bronx, Brooklyn, Queens, and Manhattan. It steps out in November.

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Queenstown International Marathon, New Zealand -

A trail marathon set in and around Queenstown, on South Island, runners are treated to spectacular scenery as they follow the 26-mi (42-km) course surrounded by mountains and lakes. It takes place in November, which is the beginning of summer in the Southern Hemisphere.

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Madeira Island Ultra Trail, Portugal - The Portuguese island of Madeira provides a scenically dramatic venue for this 71 mi (115 km) full traverse of what’s poetically described as the "Pearl of the Atlantic." The island’s stunning coastline and soaring, mist-clad mountains add to the sense of occasion. The run takes place in April, with part of the course tackled at night.

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Paris Marathon, France -

The Champs-Elysées and the iconic Arc de Triomphe mark the beginning of the 26-mi (42-km) route, which snakes through the French capital. The marathon is held every April.

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Marathon des Sables, Morocco -

Running in the Sahara Desert? You gotta be kidding! Even in April, when this blister-inducing ultra-run takes place, the heat is on. Besides an ocean of sand, competitors have to cope with razor-sharp rock and the threat of dehydration before they complete the arduous 155 mi (250 km) course.

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London Marathon, England -

Established in 1981, this is one of the world's most popular street marathons. Run every April, the 26-mi (42-km) course takes competitors past numerous well-known landmarks, including the Houses of Parliament and Buckingham Palace.

See also: The world's most extreme marathons.

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