Running 26.2 miles is crazy to begin with. So why not do it in one of the most extreme—and spectacular—places around? Sign up for a race across the alps, the outback, or icy Antarctica.
Ng Han Guan
Richard Taylor/SOPA/Corbis; Kostas Tsironis/AP; Juerg Mueller/Keystone/AP; John Carnemolla/Australia Picture Library/Corbis
