Dien Khanh Citadel

Construction in 1793

After the death of Nguyễn Huệ in 1792 the Tây Sơn weakened, and in 1793 Nguyễn Ánh advanced on Diên Khánh with Võ Tánh and Nguyễn Văn Trương^[1]. Having pushed the Tây Sơn back, he decided to turn the place into a firm base and a defensive belt held well forward of his other positions^[1].

The citadel that resulted is a military complex in the Vauban manner, the model common in western Europe in the seventeenth and eighteenth centuries^[1]. OpenStreetMap places it at latitude 12.2543 and longitude 109.0936, in Diên Khánh commune^[5].

Once the work was finished the garrison was placed under Prince Cảnh and Bá Đa Lộc^[1]. Inside the walls stood a palace, a flagstaff, the residences of the provincial governor, the judicial commissioner, the military commander and the deputy minister, storehouses and a prison^[1].

Walls, moat and gates

The rampart is an irregular hexagon of packed earth about 3.5 m high with a perimeter of 2,693 m, enclosing about 36,000 m²^[1]. VnExpress gives the wall length as 2,600 m and the area as 3.5 ha^[2]. Each side is broken into short curving sections so that the corners do not project, which still allows the defenders to watch along both faces^[1].

The outer face of the wall is close to vertical and the inner face slopes and is built in two steps, giving a route for moving men and materials around the inside^[1]. A moat 3 to 5 m deep and 20 to 30 m wide runs outside the wall^[1].

Six gates were built. Four survive: Đông in the east, Tây in the west, Tiền in the south and Hậu in the north^[1]. A single road runs from National Highway 1 through the East and West gates, and a road called Mã Xá skirts the outside of the wall between the highway and the West gate^[1]. The church of Hà Dừa stands about 200 m from the West gate; its bell tower was added by the French in 1917^[1].

Provincial seat and later use

The citadel was the political and administrative centre of Khánh Hòa province from 1802 to 1945^[2]. During the first years of the resistance to the French it served for a period as the headquarters of the Cần Vương forces in Khánh Hòa^[1].

In the modern period the district offices of Diên Khánh, including the education and training office and the police, stood inside the walls, along with a football pitch^[1]. In May 2024 the provincial People's Committee approved an administrative urban area for the district at a cost of over 2,000 billion VND, to which those offices were to move^[2].

National relic status

Dien Khanh Citadel was ranked a national historical and cultural relic in 1988^[2][4]. No fetched page gave the number of the ranking decision, only the year^[2][4].

The citadel is the largest surviving Nguyễn-period earthwork in the province and is the reason the town of Diên Khánh keeps its old street plan inside the walls^[1].

The restoration project

On 13 June 2024 the Khánh Hòa provincial development project management board, the client for the work, set out a restoration divided into twelve components at a cost of nearly 167 billion VND^[2]. The parts to be conserved in their original form include 2,500 m of earthen rampart, a crest more than 4 m wide and a brick-paved walk 2.6 m wide; new works include a road 2,000 m long and 6 m wide at the foot of the wall, an arched bridge over the moat and small parks^[2].

The clearance required for the project covered about 55,000 m² of citadel land, more than 39,000 m² held by public bodies and more than 100,000 m² in use by households^[2]. Later reporting put the land to be cleared at nearly 7.5 ha from 122 households, of which more than 7.2 ha had been recovered and about 6.7 ha was usable for building^[3]. The two accounts do not reconcile: the 2024 figures come to about 19.4 ha in all, of which more than 10 ha is household land alone, against the nearly 7.5 ha of household land in the 2026 report^[2][3].

Work began in December 2024 and the budget as reported in 2026 had risen to over 225.5 billion VND^[3][4]. Tiền Phong reported more than 65 percent of the work done as of 22 August 2026^[4], and Nhân Dân about 75 percent on 10 September 2026, with completion targeted within 2026^[3].