Thang Long was considered the biggest and oldest royal city and had the most strategic position in the history of Vietnam. In the Edict on the Transfer of the Capital issued in 1010, King Ly Thai To decided to move the capital from Hoa Lu (in Ninh Binh province) to Thang Long (in Hanoi). The royal complex was built, but due to various causes, it was damaged and buried deep under the ground.

In 2002 archaeologists began to excavate the site and found the structure and many objects of the ancient royal citadel. The Government decided to preserve the structure and its objects for future generations.

Local authorities are drafting procedures to submit to UNESCO for recognising the relic as a World Cultural Heritage Site.

The capital city of Hanoi will celebrate its millennium anniversary in 2010.