It's categorized as an ultramarathon because its length exceeds 26.2 miles (42.1 km). The full length of the marathon—five loops, roughly 20 miles (32 km) each, which must be completed within 60 hours—tends to exceed 100 miles (160 km) as the route is unmarked and gains thousands of meters of accumulated elevation.

(Photo: Flickr/CC BY 2.0)

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Barkley Marathon, USA - The race was designed by Gary "Lazarus Lake" Cantrell, who only admits 40 runners each year. Participants are selected through a secretive and unadvertised process in which entrants must write an essay on why they should be allowed to run the marathon. If accepted, they receive a "letter of condolence."

(Photo: Flickr/CC BY 2.0)

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Barkley Marathon, USA - New runners to the race must bring a license plate from their home state/country. Previous entrants who haven't finished the race must mail in a piece of clothing. For the 15 who have actually finished the race, if they run again, they must bring a pack of Camel cigarettes.

(Photo: Flickr/CC BY 2.0)

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Barkley Marathon, USA - The race has no set time—participants show up, set up camp, and wait from midnight to noon. The one-hour warning is signaled by blowing a conch, but the race officially starts when the director lights a cigarette.

(Photo: Flickr/CC BY 2.0)

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Barkley Marathon, USA - As if trying to navigate the unruly and unforgiving landscape for hours upon hours wasn't enough, runners must also find books placed along the course and remove the page in the book that corresponds to their race number as proof of completion.

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Barkley Marathon, USA - The entire race must be completed in 60 hours, and each loop must also be completed within 12 hours. With more than 1,000 competitors in the past, the entire race has only been completed 18 times, by 15 runners.

(Photo: Flickr/CC BY 2.0)

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Barkley Marathon, USA - In a somewhat cruel but hilarious fashion, the race number one is always given to the competitor who seems the least likely to complete one lap. It's said that Lazarus Lake fondly refers to them as a human sacrifice.

(Photo: Flickr/CC BY 2.0)

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Marathon des Sables, Morocco - This six-day, multi-stage race of approximately 150 miles (241 km) would be hard enough without also being in the Sahara Desert.

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Marathon des Sables, Morocco - It's considered one of the hardest races on Earth, pushing the human body to its last limits. It takes place in one of the world's driest regions featuring huge sand dunes.

(Photo: Flickr/CC BY 2.0)

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Marathon des Sables, Morocco - Even if you combine extreme heat, unfathomable distance, and tough terrain with having to carry your own food, water, clothes, and first aid kit, there are still people crazy enough to sign up.

(Photo: Flickr/CC BY 2.0)

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Big Five Marathon, South Africa - This annual race takes place every June in Limpopo Province, South Africa, otherwise known as home to the big five: rhinos, elephants, buffalo, lions, and leopards.

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Big Five Marathon, South Africa - Nothing separates competitors from beasts, and the course cuts straight through their habitat. This is not a marathon you want to pace yourself in!

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Big Five Marathon, South Africa - The Yellow Wood Valley is the most difficult part of the course for most. Runners descend an impossibly steep slope for nearly two miles (three kilometers) and, when their quads are on fire at the bottom, they find themselves in lion country!

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Big Five Marathon, South Africa - After escaping the lions, runners are faced with nearly six miles (10 km) of deep sand, after which they must climb that same steep slope from earlier. Aren't you tired just reading this?

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Western States Endurance Run, USA - One of the oldest and most popular ultramarathons in America is also one of the craziest. Runners are subjected to California's brutal summer heat while pushing themselves to run 100 miles (161 km).

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Western States Endurance Run, USA - Every June, the marathon attracts elite runners from around the world and subjects them to hours of running through Squaw Valley and the infamous Canyons—imagine 30 miles (48 km) of relentless climbs and descents in the blistering afternoon sun.

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Mount Marathon Race, USA - Quite the opposite from an ultramarathon, this Alaskan race, held every fourth of July, is less than four miles (6.4 km) long. The catch? Racers must scale an exposed cliff of 3,000 ft (914 m) before descending. The marathon has developed a rather deadly reputation.

(Photo: Flickr/CC BY-NC 2.0)

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Ultra-Trail du Mont-Blanc, France - One of the most prestigious races in the world, this stunning and iconic ultramarathon of 100 miles (161 km) starts in Chamonix, France, and takes participants to Italy and Switzerland.

(Photo: Flickr/CC BY 2.0)

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Ultra-Trail du Mont-Blanc, France - Over 2,000 top-tier international pros try their best to appreciate the breathtaking scenery as they climb thousands of feet over tricky terrain. It's one of the most festive marathons in the world!

(Photo: Flickr/CC BY-NC-ND 2.0)

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Badwater 135, USA - Running 135 miles (217 km) through California's Death Valley in July is like trying to run for hours upon hours with a blow-dryer blasting at high all over your body.

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North Pole Marathon - Guinness World Records recognized this race as the "Northernmost Marathon on Earth." A few brave souls sign up each April to run on the frozen water of the Arctic Ocean.

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North Pole Marathon - Though 26.2 miles (42 km) doesn't seem like a lot in comparison to the other marathons, runners must navigate Arctic ice floes and hard snow in temperatures that breach -40°F (-40°C).

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North Pole Marathon - People from all over the world travel up north to compete in the "World's Coolest Marathon," including blind people, elderly (the oldest was 78), and wheelchair users. The race puts them all equally on top of the world, literally.

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The Great Wall Marathon, China - Remember when you were gasping after climbing that last flight of stairs? Imagine doing that for 26.2 miles (42 km), climbing more than 5,000 steps along the Tianjin section of the Great Wall of China. Oh, and it's a race!

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The Great Wall Marathon, China - One of the most challenging marathons in the world still somehow sells out every year, with 2,500 runners traversing the iconic landmark, legs and heart ablaze.

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The Everest Marathon, Nepal - The world's highest marathon, as certified by Guinness World Records, starts near the Everest Base Camp in Nepal at an elevation of 17,000 ft (5181.6 m).

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The Everest Marathon, Nepal - The challenge begins even before the race officially commences, as competitors must first hike to the base camp and acclimatize their bodies to the altitude.

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The Everest Marathon, Nepal - All runners are welcome to take part in categories ranging from a half marathon to a 37-mile (60-km) "Extreme Ultra" marathon.

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The world's most extreme marathons

These conditions will blow your mind

11/11/18 | StarsInsider

CELEBRITY Extreme sports

Marathons are hard enough as they are, often requiring that you push your body for hours, and even days, until your lungs and legs are on fire. But for the extreme-sports minded people, a regular marathon just isn't enough. From freezing to blistering weather, highest to lowest altitudes, and terrain of all kinds, click through this gallery to see the craziest conditions people actually pay to endure.