The Mogao grottoes, a World Heritage Site near Dunhuang in western China, are located along the ancient caravan routes--collectively known as the Silk Road--that once linked China with the West. Founded by Buddhist monks in the late fourth century, Mogao grew gradually over the following millennium, as monks, local rulers, and travelers carved hundreds of cave temples into a mile-long rock cliff and adorned them with vibrant murals portraying Buddhist...