Chengdu is the fourth most populated city in mainland China and the capital of the Sichuan province and an important economic hub in western China. Chengdu's history dates back to at least the 4th century B.C., when it served as capital for the Shu Kingdom. The city is one of China’s most visited destinations, which is why the Chengdu Observatory is naturally focused on tourism and urbanization, along with post-disaster reconstruction.