WORLD'S MOST GRUELING RACE.

CYNTHIA MCFADDEN (ABC NEWS) (Off-camera) And now a journey. Far from anywhere, tourists usually tread. This trip is an intense and grueling battle. It pits man and woman against the elements and against themselves. Now, if you think running a marathon is a challenge, and I do, in a city with friends and food waiting for you at the finish line, imagine running not one, but six marathons and not nearby, but half a world away in the Moroccan Desert. People from all over the world converge to test their courage and have a real adventure. [ABSTRACT FROM PUBLISHER]