The North Pole Marathon

Who: 45 runners

When: April 9, 2015

Why it's unique: You're not just standing on top of the world, you're running anywhere from eight to ten laps around it. The 26.2-mile course, protected from polar bears by armed guards and altered every year to avoid breaks in the ice, is located near the international North Pole Camp of Barneo. The toughest challenges up in the high arctic? A chilling combination of energy-sapping footing, which gets more difficult with each pass and the temps which hover around negative 40-degrees Fahrenheit. []