Xi'an is the capital of the Shaanxi province in the People's Republic of China and a sub-provincial city. As one of the oldest cities in Chinese history, Xi'an is one of the Four Great Ancient Capitals of China because it has been the capital (under various names) of some of the most important dynasties in Chinese history, including the Zhou, Qin, Han, the Sui, and Tang dynasties. Xi'an is the eastern terminus of the Silk Road and known as the site of the Terracotta Army, made during the Qin Dynasty. The city has more than 3,100 years of history, and was known as Chang'an，literally "Perpetual Peace before the Ming Dynasty. 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. Shaanxi Province is one of the most important cradles of ancient Chinese civilization. As far back as one million years ago, some of China's earliest inhabitants lived in this region, and began spreading their culture along the life-sustaining Yellow River. Throughout the province's long history, there are 13 dynasties who established capitals here, including the Zhou, the Qin, the Han, and the Tang Dynasties. Because of this rich history, cultural relics and ruins are plentiful, and may be found preserved both above- and underground. So Shaanxi is called the 'authentic history museum' in China.