Lanzhou (, ; ) is the capital and largest city of Gansu Province in Northwest China. Located on the banks of the Yellow River, it is a key regional transportation hub, connecting areas further west by rail to the eastern half of the country. Historically, it has been a major link on the Northern Silk Road and it stands to become a major hub on the New Eurasian Land Bridge. The city is also a center for heavy industry and petrochemical industry. Lanzhou is one of the top 70 major cities in the world by scientific research output as tracked by the Nature Index. The city hosts several research institutions, including, Lanzhou University, Lanzhou University of Technology, Northwest Normal University, Lanzhou Jiaotong University, Gansu University of Chinese Medicine, and Gansu Agricultural University. Notably, Lanzhou University is one of China's prestige universities as a member of the Project 985. History Originally in the territory of the ancient Western Qiangs, Lanzhou became part of the territory of the State of Qin in the 6th century BC. In 81 BC, under the Han dynasty (206 BC–AD 220), it was taken from the Huns' Huandi Chanyu and made the seat of Jincheng commandery (jùn), and later of the Jincheng (Golden City) county (xiàn), later renamed Yunwu. From at least the first millennium BC it was a major link on the ancient Northern Silk Road, and also an important historic Yellow River crossing site. To protect the city, the Great Wall of China was extended as far as Yumen. Parts of the Great Wall still exist within the built-up area. After the fall of the Han dynasty, Lanzhou became the capital of a succession of tribal states. In the 4th century it was briefly the capital of the independent state of Liang. The Northern Wei dynasty (386–534) reestablished Jincheng commandery, renaming the county Jincheng (金城 'Gold city'). Mixed with different cultural heritages, the area at present-day Gansu province, from the 5th to the 11th century, became a center for Buddhist study. Under the Sui dynasty (581–618) the city became the seat of Lanzhou prefecture for the first time, retaining this name under the Tang dynasty (618–907). In 763 the area was overrun by the Tibetan Empire and in 843 was conquered by the Tang. Later it fell into the hands of the Western Xia dynasty (which flourished in Qinghai from the 11th to 13th century)