The remains of The Son Tay Ancient Citadel are located in the hub of Son Tay Town, Hanoi, which is in the area of two ancient villages: Thuan Nghe and Mai Trai. It was an ancient military rampart built with literate. The citadel had a style of Vauban architecture with a square shape, 400m in length and 5m in height. The citadel’s wall was 4m in width and there were many holes at the top of the wall for the soldiers to hide inside the citadel to shoot or attack their enemies using spears or broadswords.
The citadel had four gates facing east, west, south and north, namely the Front (Tien), the Back (Hau), the Right (Huu) and the Left (Ta). Each entrance has a guard tower. In the past, the citadel was surrounded by a 20m-wide, 2,000m-long moat that connected to the Tich Giang River at the southwestern corner of the rampart. The major architectural axle linked the Front and Back Gates.
Far from the citadel was La Thanh – the outside wall- which was built with mud, 3.5m high, in the shape of pentagon. It was surrounded by a spine of bamboo hedges and had four entrances facing four directions. Part of the remaining La Thanh is now La Thanh Road.
Inside the citadel were important structures that were built symmetrically on the central South-North axle. In the middle was Vong cung nu where the king could rest and mandarins in the area annually organized offering rites or bowed from a distance when they received the royal decrees.
In front of Kinh Thien Palace was a large brick-paved courtyard. Outside the entrance was a screen built with bricks and engraved with the image of “long van khanh hoi” (dragons and clouds). Next was Doan Mon with three gates looking to the Ky dai (flagpole), 18cm high, built on a large laterite platform.
To the west was Vo Mieu built to worship those who laid down their lives to protect the citadel. At the four corners of the citadel were four square wells, 6m in depth, that have steps built by laterite leading to the wells’ bottom. Nearby were residential buildings and the law courts of the provinces’ mandarins. In the east, there was a prison, a food store and the residences of the wives of the soldiers in the citadel.
In his reminiscences written in April 1884, Charles Edouard Hocquard, a French military doctor, described in detail the architecture of the Son Tay Citadel. He wrote: “…In the middle of the citadel was an 18m high flagpole. The remaining part was the royal corridors, residential buildings of the provinces’ mandarins and a food store. In front of the flagpole were two large square cisterns with their surroundings built with bricks with handrails. Many people said that one of the cisterns had been used to contain water for soldiers and the other for raising fish to serve as a food.”
In 1884, the French military army occupied the citadel and in 1924, Martial Henri Merlin, Governor-General of French Indochina, issued a decree to rank the ancient citadel as a relic. In December 1946, the Government of Vietnam Democratic Republic held an important meeting in the citadel.
After nearly 200 years, most of the Son Tay Ancient Citadel has been destroyed by wars and time and only a few relics are left, including some stretches of the citadel walls, the citadel gates, guard towers, Kinh Thien’s Palace grounds, wells and two cannons.
Because of its cultural and historical value, in 1994, the Ministry of Culture and Information recognized the Son Tay Ancient Citadel as a National Architectural Historical Relic. In 2009, Hanoi People’s Committee issued a decision to upgrade and restore some relics in the ancient citadel to celebrate the 1000th anniversary of Thang Long – Hanoi.
The Son Tay Ancient Citadel has become a unique military architectural work and cultural historical relic, attracting many tourists. Visiting the ancient citadel, tourists will also have a chance to see rows of Com nguoi (Celtis sinensis Pers) trees with a new dress of tender, young leaves in spring, Gao (Bombax ceiba) trees with red blossoms in March and wild Bo ket (Gleditsia fera) with yellow blossoms in Autumn. Tourists will surely never forget the image of hundred-year-old trees giving shade all year round and stretching their roots to cover the mossy citadel walls and gates.