While digging the foundation for a new national assembly building in 2002, workers began to unearth remnants of a much older building. Archaeologists discovered the ancient foundations of an imperial city that dates back 1,300 years to the Chinese Tang dynasty. The ancient citadel of Hanoi was the former home of Vietnamese sovereigns going back to Dai Viet, when Hanoi was known as Thang Long. Today, the ancient citadel houses the main office of the Ministry of Defence and Cot Co Tower.
Hanoi's ancient citadel was built around 1010 by the Ly dynasty and was the seat of the Vietnamese court until 1810. During colonial rule the French destroyed many structures within the citadel, including the royal palaces. Under the command of General Giap, the Vietnamese military had its headquarters in the citadel in the building known as D67. Be sure to check out the bunkers used by officials during frequent American bombing of Hanoi.