UNESCO said the site demonstrates 1,300 continuous years of Vietnamese culture. It was among the 32 sites recognised by the UN science and cultural organisation during its meeting in Brazil Sunday.

The citadel, located in the modern capital of Hanoi, was first built by the Ly dynasty in 1010. It remained the royal capital of Vietnam until 1810, when it was replaced by Hue. The ruins were discovered when workers were building the National Assembly in September 2002, the state-run Vietnam News said.

Archaeological excavations at the 40,000-square-metre site at Number 18 Hoang Dieu Street revealed four distinct periods of activity from the 7th century to the 19th century.

The citadel had apparently been re-built several times over the course of the millennium, with each construction grafted onto earlier ones. Artefacts have been well-preserved, archaeologists said.

The royal palaces and other structures were largely destroyed by the colonial French in the late 19th century, Vietnam News said. Some structures remain such as Doan Mon gate, the Flag Tower and the steps of Kinh Thien Palace.

Deutsche Presse Agentur - August 4, 2010