This 135-mile race is strictly invitation only -- and for good reason. The Badwater Ultramarathon is described as "the world's toughest foot race," and it's reserved for the best endurance athletes on Earth. It begins in the Badwater Basin in Death Valley, which is the lowest point in the United States (85 m, or 280 ft, below sea level), and ends at Whitney Portal, the gateway to highest point on tin the contiguous United States (2548 m, or 8,360 ft, above sea level) . The race takes place in a sweltering desert, during the brutal July heat. Perhaps most shockingly, the winner of this grueling race does not win any prize money -- just a simple belt buckle and the pride of accomplishment.