City wallThe most brilliant spot of this ancient town is its city wall which was originally built during 827-782 B.C. The body of the wall was first built of rammed clay, and then was enhanced by bricks and stones in the early Ming Dynasty. During the Ming and Qing dynasties, the city wall was renovated 25 times to make the inner and outer city walls strongly fortified. The sloping walls are 10m high, more than 6km in circumference and punctuated by 72 watchtowers, each containing a paragraph from Sun-tzu's The Art of War. A bird's-eye view of the city, the wall looks like a turtle, hence the name 'Turtle City'.