Cá» Loa Citadel is a fortified settlement and archaeological site, roughly 17 kilometers north of Hanoi, in the upper plain north of the Red River. Relics of the Bronze Age Phùng Nguyên culture and ÃÂông Sán culture have been found in Cá» Loa. It might be the first political center of the Vietnamese civilization. The settlementâÂÂs concentric walls resemble a snailâÂÂs shell; it had an outer embankment covering 600 hectares.
The name "Cá» Loa" is Sino-Vietnamese reading of (< Middle Chinese (ZS) kuo<sup>X</sup>-luà> Standard Chinese: gàluó), literally meaning "ancient spiral". According to ÃÂại Viá»Ât Sá» Ký Toàn Thð, the citadel is shaped like a snail, reflecting of the citadel's multi-layered structure with concentric ramparts and moats.
The site consists of two outer sets of ramparts and a citadel on the inside, of rectangular shape. The moats consist of a series of streams, including the Hoàng Giang River and a network of lakes that provided CỠLoa with protection and navigation.
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. Besides, part of the inner rampart was cut through for the purpose of archaeological investigation, which was dated from 400âÂÂ350 BCE. And it was suggested that this rampart was constructed by a local and indigenous society prior to the colonization of Han dynasty. The stamped earth technique or Hangtu method associated with ancient China may have been used in Cá» Loa, and studies of the defensive works are still in a preliminary stage. Archaeologists have estimated that over two million cubic metres of material were moved in order to construct the entire fortress, including moats that were fed by the Hoàng River. Kim estimated the population of Cá» Loa possibly ranged from 5,000 to around 10,000 inhabitants.
In 1970, the Vietnamese carried out an investigation at a collapsed portion of the outer wall, uncovering Dong Son culture sherds stratified beneath the wall. A 72 kg bronze drum was later excavated outside the inner wall in the 1980s. In 2004âÂÂ05, cultural layers were identified within the inner wall area. Cá» Loa artefacts represented "elite-level or royal characteristics", discovered only within the siteâÂÂs enclosures, supporting the notion of centralised production and monopolisation.
In 2007âÂÂ2008 another excavation took place that excavated the middle wall of Cá» Loa citadel. The excavation cut through the entire width of the rampart. The stratification showed layers of construction deposits: three periods and five major phases of construction.
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 by Nguyá» n Giang Hải and Nguyá» n VÃÂn Hùng. The drum included a hoard of bronze objects. The rarity of such objects in Southeast Asia and the range found at Cá» Loa is believed to possibly be unique. The drum stands 57 cm high and boasting a tympanum with a diameter of 73.6 cm. The drum itself weighs 72 kg and contains around 200 pieces of bronze, including 20 kg of scrap pieces from a range of artefacts. These include socketed hoes and ploughshares, socketed axes, and spearheads.
The artifacts are numerically dominated by the ploughshares, of which there are 96. Six hoes and a chisel were in the set. There were 32 socketed axes of various shapes, including a boat shaped axehead. This was almost a replica of a clay mound found in the grave of the bronze metalworker at Làng Cả. Sixteen spearheads, a dagger and eight arrowheads were also found. One spearhead generated special interest because it was bimetallic, with an iron blade fitting into a bronze socket.