Excavation of Yan Capital Site(燕都城遗址Yāndūchéng yízhĭ) of Early Western Zhou Dynasty in Liulihe Town, Fangshan District, Beijing(City) announced to the world the discovery of capital of Yan state in Western Zhou Dynasty. In early Zhou dynasty, Yan was one of the important vassal states of vast territory in the north. Located at Liulihe Town, Fangshan District, Beijing, the ancient Yan capital named Pingming takes the shape of a rectangle.

The city wall made of ocher(ocre) reaches as long as 829 meters in the north and an extant length of about 300 meters from east to west. Outside of the wall lies an over two-meter deep moat(a deep, wide channel dug round a place such as a castle and filled with water, in order to protect the place from attack).