Lying in northwestern China, the Xinjiang Uygur Autonomous Region, also called Xin for short, was referred to as the Western Region in ancient times. It has an area of 1.66 million square kilometers, roughly about one-sixth of the total territory of China. Xinjiang is the largest and has the longest boundary line among China's provinces and autonomous regions. It shares 5,600 kilometers of frontier with Mongolia in the northeast; Russia, Kazakhstan, Kirghiszstan, and Tadzhikistan in the west; and Afghanistan, Pakistan, and India in the southwest.