Hexi Corridor or Gansu Corridor refers to the historical route in Gansu province of China. As part of the Northern Silk Road running northwest from the bank of the Yellow River, it was the most important route from North China to the Tarim Basin and Central Asia for traders and the military. The corridor is a string of oases along the northern edge of the Tibetan Plateau. To the south is the high and desolate Tibetan Plateau and to the north, the Gobi Desert and the grasslands of Outer Mongolia. At the west end the route splits in three, going either north of the Tian Shan or south on either side of the Tarim Basin. At the east end are mountains around Lanzhou before one reaches the Wei River valley and China proper.