Xi'an (formerly Chang'an) was the imperial capital of China for no less than 11 dynasties from 1000 B.C. to 1000 A.D. and was the eastern terminus of the fabled Silk Road. It reached its golden age during the Tang Dynasty (7th to 10th centuries A.D.), when the city's population grew to more than a million inhabitants.
Xi'an is nowadays a modern metropolis of some 5 million people but the Old City Walls are still largely intact and there are several interesting historical sites worth seeing. You will visit the Bell Tower, originally built in the 14th century though much restored, the Muslim Quarter, the Big Wild Goose Pagoda (pictured) and the impressive Shaanxi History Museum, well laid out and with English captions.