Summertime endurance events tend to have split personalities. One of those—the gentle, pleasant side—is defined by the breathtaking panoramas in which these competitions take place. From the red rocks of Moab to the throngs of butterflies in Montana’s high country, the venues are spectacular. But there is of course the other personality, the one that makes lungs pop and legs scream for mercy. Oxygen-deprived air, uneven terrain, scorching daytime sun and frigid nighttime air—the landscapes are as majestic as the events are brutal. But when these personalities team up, they offer experiences that competitors never forget.