The City Walls, ramparts, gates and watchtowers form one of the oldest and most complete city defences still around. Built in the 13th century on the foundations of the original Tang Forbidden City surrounding the city centre you can walk, rent a bike or take an electric cart around the full 14km circuit, with great views of the city on either side.
The Tang dynasty built its capital Chang'an 7km/4.5 miles north-west of where Xi'an lies today. Its defensive walls, 22km/14 miles in length, formed an irregular quadrilateral with twelve gates, each with three entrances. The main gate was reserved for the use of the emperor. The north side of the wall is shaped rather like the Ursa Major constellation, and the south side like Ursa Minor.

The town was served by eight main streets and 160 side streets together with large numbers of palaces (none of which survive) and an excellent drainage and sewage system using pentragonal clay pipes. On the excavation site, in addition to the remains of the town walls to the south-west, the visitor can still see a large mound of earth which is all that is left of the Han imperial residence, the Palace of Weiyang, around which countless legends have been woven.

At one time the palace comprised more than 40 separate buildings, the main one being 183m/600ft long, 164ft wide and 12m/39ft high. During the Tang era (618-907) what is now Xi'an formed a part of Chang'an, which at that time was 37km/23 miles in circumference and had a population of a million or so. The town was divided into two parts. The inner embraced the northern district with the imperial palace and the southern with the seats of government and administration, while the outer part, lying to the east, west and south of the inner districts, was where the ordinary people lived.

Its 25 main streets were lined with numerous markets, shops and workshops. Archaeological research indicates that the western section of the town wall was 2656m/2920yd long, the northern 1135m/1248yd and the eastern (divided into three sections) 2610m/2870yd.