If you combined the endurance demands of the New York Marathon with the grueling climate conditions of the Alaskan Iditarod, you'd get a sense of the Dutch ice-skating race called the Eleven Cities Tour.
Known as the Elfstedentocht in Dutch, the one-day tour is an obsession for its 16,000 participants and the millions more who follow it worldwide. The event is held in The Netherland's northern province of Friesland but only in those years when the ice freezes over the 124-mile track of lakes and canals that makes up the route. The last tour took place January 4, 1997.