Goachang is the largest city ruin in west China. The site served as the economical and religious center of Asia is located 40 kilometers from the Turpan City, at the north bank of the Aiding Lake and to the south of the Flaming Mountain.

Gaochang was fertile and cultivated land and served as capital of three western states. From the historical documents and relics excavated in the region, historians are able to sketch the outline of this grand city. Gaochang�s ideal location at the middle of the Turpan Depression and the city�s well layout with high walls and deep moats made it a significant military fortress of the Western Region over years.

Founded in the Liang Dynasty, Gaochang became part of the Tang�s territory from 640 under Emperor Taizong. The city saw frequent changes of dynasties in the following hundreds of years and it was fatally destroyed during wars launched by Mongols in 12th century. It was later abandoned and became a ruins.�
The ruins cover around 2.2 million square meters, containing three parts: the outer and inner cities. The layout of the city is similar to that of Chang�an, capital of Tang Dynasty at that time. The outer wall is the only visible structure left today. Some parts are well-preserved. The wall is about 5.4 kilometers long and up to 11.5 meters high. The foundation of the wall is as thick as 12 meters which make the structure very solid and strong. At the southeast and southwest sections of the Outer city stands many temples ruins.

The Inner City is rectangle-shaped and stretches around 3,600 meters long. Architecture inside the Inner City mainly was temples and palaces. The palace complex is in the middle of the Inner City and share the north wall with the outer City. There were many high and grand building in the complex but they are all very difficult to discern in its current state.