Gansu is a province located in the northwest of China. It lies between the Tibetan and Loess (黃土高原) plateaus, and borders Mongolia, Inner Mongolia, and Ningxia to the north, Xinjiang and Qinghai to the west, Sichuan to the south, and Shaanxi to the east. The Yellow River passes through the southern part of the province.
Gansu has a population of 26 million and has a large concentration of Hui Chinese. The southwestern corner of Gansu is home to a large Tibetan population. The capital is Lanzhou, located in the southeast part of the province.
In imperial times, Gansu was an important strategic outpost and communications link for the Chinese empire, as the Hexi corridor (河西走廊) runs along the "neck" of the province. The Han dynasty extended the Great Wall across this corridor, also building the strategic Yumenguan (Jade Gate Pass, near Dunhuang) and Yangguan (阳关) fort towns along it. Remains of the wall and the towns can be found there to this date. The Ming dynasty also built the Jiayuguan outpost in Gansu. [Source: Wikipedia]