The Imperial Citadel of Thang Long is a historic site that served as the epicenter of Viet Nam’s political power for centuries. It is located in Hanoi, within Ba Dinh District. Its core heritage area covers 18.395 hectares, with an additional 108 hectares designated as a buffer zone.
Physically, the citadel consists of several layers of historical zones. The front section is marked by the Flag Tower and the Doan Mon Gate with its five arched doorways. Deeper inside lies the courtyard of the Kinh Thien Palace, which once housed the imperial throne, alongside the archaeological excavation site on Hoang Dieu Street.
A Hub of Power Across Dynasties
Long before its construction by the Ly Dynasty in the 11th century, the site was originally a military headquarters for China’s Tang Dynasty, established in the 7th century.
The construction of the imperial citadel began in 1010 when King Ly Thai To relocated the capital of the Dai Viet Kingdom from Hoa Lu. The new location was named Thang Long, meaning "Ascending Dragon."
For nearly eight centuries, Thang Long served as the primary seat of government for the Dai Viet Kingdom. During the Tran Dynasty in the 13th century, the citadel’s wall structures were reinforced to withstand three waves of Mongol invasions.
From the 15th through the 18th centuries, the Le Dynasty continued developing the complex by erecting the Kinh Thien Palace and expanding the layout of the imperial city.
As ruling dynasties changed over time, Thang Long consistently maintained its position as the administrative center of the Dai Viet Kingdom.
A major shift occurred when the Nguyen Dynasty ascended to the throne in 1802 and chose to move the capital to Hue in central Viet Nam. Although its status as the imperial capital came to an end, the citadel complex was far from abandoned.
The Nguyen Dynasty renovated the outer walls using French Vauban-style fortification architecture, converting the complex into a military command center to oversee northern Viet Nam.
Shift to a Military Headquarters
When the French occupied Hanoi in the late 19th century, the function of the complex transformed once again. The colonial government demolished most of the ancient palaces within the citadel to level the ground and build new military barracks and facilities.
Amidst the wave of demolition, several imperial-era structures survived. The Doan Mon Gate, which previously served as the main entrance to the Kinh Thien Palace, was preserved along with its five arched passages.
Nearby, the Hanoi Flag Tower—built by the Nguyen Dynasty in 1812—also survived. The structure was utilized by the French military as an urban observation post until the end of the colonial period.
When the Viet Nam War broke out, the citadel complex was repurposed as a headquarters by North Vietnamese forces. In 1967, the government constructed an underground command center known as Bunker D67.
The facility was built nine meters underground using reinforced concrete. From this bunker, leaders of the Politburo and the People’s Army of Viet Nam planned war strategies until the conflict ended in 1975.
Following the reunification of Viet Nam in 1975, the citadel complex remained in use as a headquarters and office for the Ministry of National Defense.
The process of opening the site to the public began in 2002, when the military handed over portions of the land to the city government ahead of planned construction for a new parliament building at No. 18 Hoang Dieu Street.
Artifact Discoveries Leading to UNESCO Recognition
The plan to build the parliament building initiated a series of archaeological excavations. The government appointed a research team to survey a 4.8-hectare area before construction began.
During the digs, archaeologists unearthed numerous buried relics, including brick drainage systems, bronze coins, and imperial ceramic fragments from various dynastic eras.
The underground findings complemented the structures remaining on the surface, such as the stone dragon staircase built in 1467 at the Kinh Thien Palace.
The evidence of multi-layered heritage within a single area was a key factor in UNESCO designating the citadel as a World Heritage Site in 2010. The designation coincided with the 1,000th anniversary of the founding of Hanoi.
Today, the entire citadel is protected as a cultural heritage site open to the public.
