The center’s director Nguyen Van Son said that if the proposal is approved, the center will compile the file immediately. The UNESCO will make a decision 18 months after it receives the file.

Son said many domestic and foreign experts highly appreciate the cultural and historical values of the Co Loa Relic so it is highly possible for the relic to be recognized as a world cultural heritage.

Co Loa Citadel is a citadel built about 20km to the north of Hanoi, during the end of the Hong Bang Dynasty (about 257 BCE). The fortress is a spiral-shaped complex of the then new capital. The site has been the source of various relics of the Dong Son culture of the Bronze Age.

According to folklore, An Duong Vuong defeated the last of the Hung kings in 257 BCE and founded the kingdom of Au Lạc, choosing the site of Co Loa as his capital.

Co Loa is a very large site and is the dominant presence in the northern floodplain of the Red River Delta, which would have required a large amount of labor and resources to have built in its time.

The site consists of two outer sets of ramparts and a rectangular citadel on the inside. The outer rampart comprises a perimeter of 8 km and is lined with guard towers. The ramparts still stand up to 12 m high and are 25 m in width at their base.

Archaeologists have estimated that over two million cubic meters of material were moved in order to construct the entire fortress, including moats that were fed by the Hoang River.

Excavations made by archaeologists have revealed Dong Son style pottery that had stratified over time under the walls, while a drum was found by chance. The drum included a hoard of bronze objects. The rarity of such objects in Southeast Asia and the range found at Co Loa is believed to possibly be unique.

The artifacts are numerically dominated by the ploughshares, of which there are 96. Sixteen spearheads, a dagger and eight arrowheads were also found.

Hanoi currently has four world heritages recognized by the UNESCO: Thang Long Royal Citadel, Van Mieu doctoral stone steles, ca tru folk songs and Saint Giong Festival.