One of the most difficult of all races in the world is the Marathon des Sables, a 235-kilomater race though the Sahara Desert. It has six stages over seven days. It includes a marathon race as well as a day where the participants run up and down large walls of sand. Many respond to the challenge of running in the harsh environment. Mauro Prosperi, an Italian police officer and experienced marathon runner, was running in the race and was running well, in seventh place, when a sandstorm kicked up. Clouds of sand covered the course, and it was impossible to see ahead. Prosper wrapped a towel around his face and he tired to keep running. Soon, however, he had to look for shelter under a bush.