The Tang dynasty or the Tang Empire (Chinese: ) was an imperial dynasty of China preceded by the Sui dynasty and followed by the Five Dynasties and Ten Kingdoms period. It is generally regarded as a high point in Chinese civilization, and a golden age of cosmopolitan culture. Its territory, acquired through the military campaigns of its early rulers, rivaled that of the Han dynasty, and the Tang capital at Chang'an (present-day Xi'an) was the most populous city in the world.

Answer this question based on the passage: the capital of the tang dynasty and the largest city in the world at the time was? Okie... think carefully first, then make a decision:
This is the relevant information: Its territory, acquired through the military campaigns of its early rulers, rivaled that of the Han dynasty, and the Tang capital at Chang'an (present-day Xi'an) was the most populous city in the world. So, the answer is Chang'an ( present - day Xi'an ).