4. Xi'an

Xi'an, the capital of China's Shaanxi province, was known as Chang'an before the Ming Dynasty (1368-1644). It is one of the Four Great Ancient Capitals of China, with a history spanning over 3,100 years. It used to be the capital of the most important dynasties in Chinese history, including the Zhou (1046-256 B.C.), Qin (221-206 B.C.), Han (202B.C.-220A.D.), Sui (581-618), and Tang (618-907) Dynasties. The city is the eastern terminus of the Silk Road and home to the Terracotta Army. It is known as a "natural history museum."