There were six capital cities. The main capital was called Chang’an and occupied the area where Xi’an and Shaanxi are located in modern China. The central capital was called Zhongdu and occupied the area where Yongji and Shanxi are located.
To the east, the captial was called Dongdu and occupied the area where Luoyang and Henan are now located. On the western side, the capital city of Xidu was located in parts of China now occupied by Fengxiang and Shaanxi.
To the south was the capital city of Nandu occupying parts of Chengdu and Sichuan, and to the north, the capital city of Beidu which occupied parts of Taiyuan and Shanxi.
There was also an eastern (Andong), northern (Anbei), western (Anxi) and southern (Annan Duhufu) protectorate which kept the peace.
The Tang Dynasty spread across much of what is now modern China and is considered to be the high point in Chinese civilization.