Kinh An Dương established the capital of Âu Lạc in Tây Vu, where a fortified citadel is constructed, known to history as Cổ Loa. It was the first political center of the Vietnamese civilization pre-Sinitic era, with an outer embankment covering 600 hectares, one of the largest prehistoric settlement sites of Southeast Asia. This name was derived from the Sino-Vietnamese , meaning "old spiral", reflecting its multi-layered structure of earthworks, moats and ditches. However, according to Dr. Lê Chí Quế, "Cổ Loa" is spelled of Old Vietnamese word "k'la" () means "chicken". It corresponds to the legend of the white chicken that stalled the construction of the citadel. Near Cổ Loa commune there is an old site that was Chicken village (). This site coincides to the legend that belonged to one tribe's totem.