As famed grand tours of summer such as the Tour de France roll through Europe on carbon frames and ultra-light wheels, a number of lesser-known, if more rigorous, races are also gearing up to go. They include cycling and foot races that take athletes through some of the world's most spectacular and rugged country, as well as to the boundaries of what humans can endure, physically and psychologically.
The more demanding of them allow no rest or sleep--unlike the more publicized stage races -- and amount to nonstop endurance tests lasting as long as a week or more. Some of them also allow almost anyone to enter, in case you're interested in trying your muscles in what might be the most unenjoyable tour you'll ever take of the Sierra Nevada, the Rocky Mountains, the American desert or the Australian outback.
Here are the top five extreme race options for your next vacation: