Xi'an (; Postal map spelling: Sian), is the capital of Shaanxi province in People's republic of China and a sub-provincial city. As one of the most important cities in Chinese history, Xi'an is one of the Four Great Ancient Capitals of China for it has been the capital of 13 dynasties, including the Zhou, Qin, Han, and the Tang. Xi'an is also renowned for being the eastern terminus of the Silk Road and for the location of the Terracotta Army made during the Qin Dynasty. The city has more than 3,100 years of history. It was called Chang'an () in ancient times. Since the 1990s, as part of the economic revival of interior China especially for the central and northwest regions, the City of Xi'an has re-emerged as an important cultural, industrial and educational center of the central-northwest region, with facilities for research and development, national security and China's space exploration program. Origin of Name