The Nguyen dynasty named the country Dai Nam with its capital in Hue; in the midst of a gradual power consolidation and rebuild of the country, after defeating the Tay Son dynasty. They established Bac Thanh as the administrative region, which included 11 provinces and Thang Long as the centre. However, the name Long 龍 (Dragon) was replaced with its homophones Long 隆 (Prosperous) and the head of Bac Thanh was a governor. In 1831, Minh Menh reformed the country’s administration and Bac Thanh was changed into Hanoi province. Thang Long at that time was the provincial capital of Hanoi province.

After claiming sovereignty over the country and Thang Long, the Nguyen court realized that the old buildings of Thang Long Capital under the Le Trung Hung period was seriously degraded. Therefore, the Nguyen dynasty rebuilt Thang Long with a new role as the capital of Bac Thanh town, then Hanoi province.  The rebuild also sought to meet the multifaceted requirements of the new era in defence technology such as the changes in citadel construction techniques, new military techniques of the world such as the proliferation of fortified citadels, firearms, warships along with the East-West cultural interchange.In 1803, Emperor Gia Long of the Nguyen dynasty demolished the Imperial Citadel of Thang Long (built in the Le Trung Hung period) to make room for a new citadel in the Western star fortress style with a general square plan. On the field today, vestiges of the walls of Hanoi under the Nguyen dynasty are identified at the following locations:North side: Parallel to the current Phan Dinh Phung street, there is still the Chinh Bac (Northern) gate with three Chinese characters written on the gate of the city "Chinh Bac Mon", located opposite Dang Dung street.South side: Around Tran Phu street.West side: Parallel to the current Hung Vuong street. Hung Vuong street is located on the inner slope of the wall. Chinh Tay (Western) Gate is located at the current position of Ho Chi Minh Mausoleum. Archeologists have found traces of wall foundations and a moat at Chinh Tay gate and southwest corner.

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Map of Thang Long - Hanoi during the Nguyen dynasty 

Source: Institute of Archeology

East side: Coinciding with the current Phung Hung street. The main gate of the East is located at the junction of the beginning of Cua Dong street and Ly Nam De street.In the citadel, there are roads in two axes North-South and East-West. In the north-south direction, there are five routes, two main routes (coinciding with Hoang Dieu and Nguyen Tri Phuong) divided into three areas: the central area, the eastern area and the western area, the remaining two routes are in close proximity to the eastern edge (Ly Nam De street today) and the western edge of the citadel (now Doc Lap street). In the east-west direction, there are four routes that are relatively evenly spaced (including 3 routes coinciding with the current Le Hong Phong, Bac Son - Cua Dong and Hoang Van Thu roads). These routes intersect to form squares (20 squares) of checkerboard style.Olivier Tessier calculated the total perimeter of the citadel to be 5,728m and the total area at ​​110,000m2. The wall is 5m high, the moat is 15m to 18m wide and 5m deep (Olivier Tessier, From Thang Long to Hanoi: Demolition and destruction of the Imperial Citadel in 19th century, in Revealing the Imperial Citadel of Thang Long, the first glimpse of Hanoi's archaeological heritage World Publishing House, 2018: 288 - 289).Outside each gate used to lie a Duong Ma wall (“Goat and Horse wall”, also known colloquially as Mang Ca- Fish Gill or Giac Thanh- Corner Wall) - a type of fortification consisting of two perpendicular walls protruding outward to protect the citadel. Each Duong Ma wall has a side portal about 1 truong (4m) wide called Nhan Mon (Human’s entrance). From the outside one has to go through Nhan Mon and then the main gateway. Such a layout makes it easy for the guards to defend.In parallel with the construction of a new citadel that was completely different from the traditional architecture as the result of the East-West cultural exchange process, the Nguyen Dynasty according to feudal protocols gradually destroyed the old symbolic architectures of the Le Trung Hung dynasty. They built new symbols of their era: In 1806, Xa Tac Altar was built near the West gate.In 1812, built the Flagpole (Ky Dai). In 1815, the Le Trung Hung period’s Kinh Thien Palace was dismantled, and Phan Vong hall was built in its place.In 1821, Tinh Bac tower (Hau Lau) was erected.In 1822, a shrine to the deceased emperors was founded.In 1835, the wall of Hanoi was lowered by 0.72 cm.In 1841, the name of Phan Vong hall was changed to Long Thien Palace.

Thus, the Hanoi citadel under the Nguyen dynasty was built on the basis of the Thang Long citadel of the Le Trung Hung period. But the planning in 1821-1831 described in Dai Nam Nhat Thong Chi (Dai Nam’s Comprehensive Encyclopaedia) and the map of the Nguyen dynasty clearly shows how the Axial planning and their ramifications in Hanoi citadel is still the traditional capital layouts of Vietnam and the East. Notably, in the new plan, the bases of the Doan Mon gatehouse and Kinh Thien palace of the Le Trung Hung period and the palace’s dragon-decorated steps were still retained. At the Thang Long Imperial Citadel Heritage site, some relics are still standing on the surface (Bac Mon, Ky Dai) and archeologists also discovered traces of Duong Ma wall and the southwest corner moat at 62-64 Tran Phu street, some vestiges of the foundation of the fortifications, the palace in the main area of ​​Kinh Thien Palace.

It can be said that the Hanoi citadel under the Nguyen dynasty was a continuation of the Thang Long citadel of the Ly, Tran, Le, Mac, and Le dynasties. The scale of this citadel, as determined by researchers, is roughly the same as that of the Forbidden Citadel of Thang Long under the Ly-Tran-Le dynasties (maybe slightly larger or smaller). Newly erected buildings were numerous. In the process of demolishing Thang Long citadel, the Nguyen dynasty still retained a few important relics of the Le Trung Hung period such as Doan Mon gatehouse, vestiges of Kinh Thien palace with relatively intact stone steps from the Le So dynasty. This collection of relics has been recognized as a National Treasure by the Prime Minister in 2020.The new citadel reflected its epochal features with its "Star fortress" layout and "Vauban" technique- ubiquitous in the world at the time. The wall is built of bricks with advanced traditional construction methods. Although new features were apparent, the buildings were still steeped in traditional, which is reflected in the liberal use of bricks, the construction of the wall foundation, the pile footings, the radial layout and the vertical axis, all according to the layout principle of Vietnamese traditional architecture.

                                                          Thanh Thuý - Ngọc Hòa