The Barkley 100-Mile Marathon, held annually in Frozen Head State Park near Wartburg, Tennessee, is considered to be one of most challenging ultra-marathons in the world. So tough, in fact, that only 14 people out of about 1,100 participants have ever managed to complete it since its inauguration in 1986! That's just two more than the number of people who have walked on the moon.
The 100-mile run, which some claim is actually 130 miles or more, has a cumulative elevation gain of more than 60,000 feet - the equivalent of climbing mount Everest twice, from sea level. It consists of a 20-mile loop around a mountainous course that participants need to complete five times. Loops three and four need to be run in the opposite direction, with the direction for loop five being the runner's choice. Experienced runners looking for something less extreme can opt for the 60-mile 'fun run', where they have to run the 20-mile loop just three times.
