A worker stands on a construction site of the national highway G219, or the Xinjiang-Tibet Highway, in Qitai county of Xinjiang Uygur autonomous region, May 3, 2011. The construction has entered its toughest phase, working at an altitude of nearly 5,000 meters, and an average temperature of -5 C. The 120-kilomenters of frozen soil and more than 100 days of gale force winds annually also add to the difficulty of the project. [Photo/Xinhua]