Yangguan, or Yangguan Pass (traditional Chinese: 陽關; simplified Chinese: 阳关; literally: "Sun Gate"), is a mountain pass that was fortified by Emperor Wu of the Western Han Dynasty around 120 BC and used as an outpost in the colonial dominions adjacent to ancient China. It is located approximately 70 kilometres (43 mi) southwest of Dunhuang, in the Gansu territory to the west of the Shaanxi province in the far Northwest China, which was in ancient times the westernmost administrative center of China. It was established as a frontier defense post, as well as a developed place in China's remote western frontier; Emperor Wu encouraged Chinese to settle there.