河西回廊
The Mongol Steppe includes both Mongolia and the Chinese province of Inner Mongolia. The two are separated by a relatively dry area marked by the Gobi Desert. South of the Mongol Steppe is the high and thinly peopled Tibetan Plateau. The northern edge of the plateau is the Gansu or Hexi Corridor, a belt of moderately dense population that connects China proper with the Tarim Basin. The Hexi Corridor was the main route of the Silk Road. In the southeast the Silk Road led over some hills to the east-flowing Wei River valley which led to the North China Plain.