Xi'an is located in the guanzhong Basin of the middle section of Yellow River Valley in the center area of mainland China. The total area of Xi'an is 9,983 square kilometers. Qinling Mountains span in the south of the city, and the absolute altitude of its ridge is 2,000-2,800 meters. Also it is an important geographical dividing line of South and North China. To the north of Xi'an, along the border of Huangtu Highland, the Beishan mountain system consist of Liang mountain, Yellow Dragon Mountain, Yaowang Mountain and Long Mountain which echo one another at a distance with Qinling Mountains, which forms a barrier around the Guanzhong Plain. Wei River, the largest branch of Yellow River, flows across Guanzhong Plain. Guanzhong Plain came into being due to the alleviation of Wei River and its branches, so it is also called Weihe Plain. The Plain begins from Baoji in the west, and reaches the Yellow River in the east, known as "800-li Qinchuan'.