The discovery, a century ago, of the Library Cave at the Mogao Grottoes in Dunhuang astounded the entire world. Throughout Dunhuang's history over two thousand years, it has always served as a critical gateway to the west, because of its unique geographical location at the juncture of Gansu, Qinghai and Xinjiang. As a result, throughout the Chinese long history, several emperors have made improvements of these western fortifications. However, Dunhuang was also a regional cultural center. The Mogao Grottoes, also known as the Dunhuang Grottoes or the "Thousand Buddha Grottoes", is located on the western cliffs of the Singing Sands Mountains. It is one of the most complete collections of Buddhist frescoes and sculpture from a period range over ten dynasties.