A look at more than 60 of the most extreme marathons, triathlons, bike rides, and other iconic endurance events from around the globeEach year, thousands of competitors pit themselves against the elements, extremes of geography, and their own psyches to take part in the world's hardest physical challenges. From the cold of the highest peaks to the unforgiving heat of the desert, by sea, bike, or foot, seemingly ordinary people are undertaking extraordinary feats. Whether seeking to prove themselves as athletes, or attempting to escape the humdrum, one thing they all have in common is an...