Contestants' lamps illuminate the trail at the start of the Glacier Patrol, or Patrouille des Glaciers, on Wednesday. The 53-kilometer (32-mile) track along the Swiss-Italian border is considered one of the most difficult high-mountain races in the world. The contestants, who compete in patrols of three, race on foot and by ski from the shadow of the Matterhorn (pictured) in Zermatt to Verbier.