Dunhuang was of great importance as a defensive and cultural center on the western borders of the Chinese empire at various points in its history. The routes west going north and south of the Taklamakan Desert split near Dunhuang. The route to the south and southwest was guarded by the so-called "Jade Gate" (Yü Guan) and "Southern Gate" (Yang Guan) which were garrisoned and supplied from Dunhuang. The Dunhuang region was the site of very important Buddhist monastic complexes, the most famous of which was at the Mogao Grottoes, where today one can see a treasure trove of Buddhist art covering a span of more than a millenium.
Here are some materials on Dunhuang and its region; they include image maps, which allow one to select a location on the map and click on it to bring up additional description and images.