Alaska
Photo credit: Marc Lester / Anchorage Daily News / AP
For any runners out there who are thinking, "Sure, jogging endlessly until my lungs give out and my toes bleed is fun, but I need something more challenging than a regular marathon," there's Alaska's Mount Marathon. The race, which has been held each July 4 since 1915, runs right up the side of a large mountain in Seward. Thousands of willing participants — for reasons unclear — dash 1.5 miles up the mountain, past cliffs and waterfalls, then 1.5 miles back down. The adult record holder managed to do it in just over 43 minutes. Doesn't sound daunting enough? Check out this line from the official entry form: "Be prepared to get yourself down the mountain, even if injured." Gotta love that frontier spirit. Entry fee: $45