The Citadel of Hanoi was the former residence of Vietnamese monarchs dating back to the 'Dai Viet'鈥攖he period of great Vietnamese dynasties when the city was known as Thang Long.

The citadel was constructed by the Ly Dynasty in 1010 CE and remained the seat of the Vietnamese court until 1810; when Hue became the capital city. The royal palaces and other various structures were largely destroyed by the colonial French in the late 19th century.

During the Vietnam War (American War); the North Vietnamese military command under General Giap had its headquarters in the citadel in a building known as D67. An underground tunnel enabled the military to flee in case of a raid.

Construction work for the National Assembly building in 2003 uncovered large remains of the citadel dating back to Thang Long; some of which are now exhibited in the Vietnamese History Museum. In 2010; the citadel was inscribed on the UNESCO World Heritage List as 'The Central Sector of the Imperial Citadel of Thang Long鈥擧anoi'.