The Site of Yan City is located to the west of the Hutang Bridge in Wujin County -- about seven kilometers from the south gate of Changzhou City, Jiangsu Province.

The site covers an area of about 67 hectares, 47 of which are arable land. It comprises three rings of constructions: the outer city, inner city and a small city within a larger one. It also has three rings of moats. The outer city is an irregular, round shape with a perimeter of 2,580 meters. It has a diameter of 800 meters from east to west and 750 meters from south to north. The remnants of the city wall are about 10 meters high and a width varying from 25 to 50 meters. The city moat is 40 to 50 meters wide and over three meters deep. The inner city is square in shape with a perimeter of 1,252 meters. It is 20 meters wide and 10.5 meters high -- much higher than the outer city. The small inner city was a palace, also known as Ziluo City, located in the central north of the inner city. Also square-shaped, the inner city has a perimeter of 457 meters and is 11 meters high and seven to 10 meters wide. The three cities each have a gate and a city moat surrounding them outside.

Historical records and cultural relics from the site suggest that, including three dugout canoes, bronze plates, celadon and pottery with geometry patterns, the site should have been built during the Western Zhou Dynasty (11th century - 771BC) or the Warring States Period (475-221BC).

Judging from the city's scale and facilities, it does not resemble an imperial palace but a fortress where troops were stationed. The well-preserved site provides precious data into the study of the Western Zhou and Warring States Period cities.