An overnight stop in Urumqi (there's even a Holiday Inn) gives a chance to see the museum there at leisure. Especially the famous mummies, perfectly preserved by the dry desert air in the tombs of the region, and the variety of grave goods, textiles and designs in the tombs that testify to the mixing of races and cultures that took place in Central Asia.
Surrounded by a harsh landscape, the oasis town of Turpan (or Turfan) is easily accessible by road or rail and is on most tourist itineraries. The seventh-century monk Xuan Zang stopped there, on his way to India, and found the king's hospitality impossible to refuse. He had to go on hunger strike to be allowed to continue his journey.
Turpan stands in the midst of a basin which boasts the second lowest spot on earth: 154 meters below sea level, hence the extremes of temperature (-15 to 40 C).