Lanzhou is the capital and largest city of Gansu Province in Northwest China. A prefecture-level city, it is a key regional transportation hub, allowing areas further west to maintain railroad connections to the eastern half of the country. Lanzhou is home to 3,616,163 inhabitants at the 2010 census and 2,177,130 in the built-up area (urban) on 1,088 km².
Lanzhou is situated on the upper course of the Yellow River, where the river emerges from the mountains. It has been a center since early times, being at the southern end of the route leading via the Hexi Corridor across Central Asia. It also commands the approaches to the ancient capital area of Chang'an (modern Xi'an) in Shaanxi province from both the west and the northwest, as well as from the area of Qinghai Lake via the upper waters of the Yellow River and its tributaries.