Co Loa Citadel was built near Phong Khe, about 20 km to the north of Hanoi today. Covering nearly 500 hectares, the citadel was a place of worship for King An Duong Vuong and Princess My Chau, who are mentioned in the magic crossbow legend that has been woven into the history of Vietnamese people. A strong army might have been mobilised to build Co Loa, according to historians. (Photo: VNA)

According to folklore, Thuc Phan (King An Duong Vuong) defeated the last of the Hung kings in 257 BC and founded the kingdom of Au Lac, choosing the site of Co Loa as his capital.

Co Loa is a very large site and is a dominant presence in the northern flood plain of the Red River Delta, so building it would have required a large amount of labour and resources.

The story goes that when the citadel was built, all work done during the day was destroyed at night. The king made a sacrifice and that night Than Kim Quy (Gold Turtle God) came to him in a dream and told him that he was building the citadel on the turtle's carapace. The turtle god instructed him to build the citadel in a new location, that of present-day Co Loa. The king did so, and the citadel was soon finished. (Photo: VNA)

Co Loa Citadel covers the three communes of Co Loa, Viet Hung, and Duc Tu in Dong Anh district. It is in the shape of a conch shell and had nine walls, each protected by a moat. The moats were part of a series of streams and lakes that exist to this day and provided Co Loa with protection and navigation.

Out of gratefulness to the king, the magic turtle gave the king a toenail that he could use as a trigger on his crossbow. When used, it multiplied its force by thousands and could kill thousands of enemies at one time. An Duong Vuong was so fond of the crossbow, always hanging next to the place he lay. (Photo: VNA)

Sitting on a mound shaped like a dragon's head, An Duong Vuong Temple is surrounded by two forests on both sides, below there are two round holes called dragon eyes. According to legend, one of the Qin dynasty leaders, Zhao Tuo, took advantage of the decline of the Qin and created his own kingdom north of Au Lac. He tried to conquer his southern neighbour but was repeatedly defeated, so he had to wait for the opportunity. He later sent his son, Prince Trong Thuy, to negotiate a peace treaty and ask for the hand of Princess My Chau, An Duong Vuong’s daughter, in marriage. My Chau carelessly told her new husband about the crossbow, who then stole it and replaced it with a fake one, leading to a devastating defeat against Au Lac. (Photo: VNA)

The large lake in front of the temple. Inside the lake is Trong Thuy Well, also known as Ngoc Well, where, according to legend, Trong Thuy committed suicide. Fleeing his enemies, King An Duong spotted his daughter leaving a trail of goose feathers for Trong Thuy to follow. The King came to his senses, pulling out his sword and beheading My Chau.

Stories of the Thuc king's demise vary. Some say he committed suicide by jumping in the ocean. Some say he was borne off to sea by the magic turtle and never seen again. Some say he was told of his daughter's betrayal by the magic turtle and killed her before disappearing with the turtle. Trong Thuy, for his part, found My Chau shortly after and, overwhelmed with grief, drowned himself in a well in Co Loa Citadel. (Photo: VNA) 

It is said that there were nine rings, a deep water trench surrounded in an outside circle.

Nowadays, Co Loa Citadel remains as three land rings: outside citadel, the middle citadel and inside citadel. The citadel wall today has average height of 4-5 meters, some reach to 12 meters high; the citadel’s foundation is 20- 30 meters wide. Archaeologists found thousands of bronze arrows, plows, axes, animal bones, etc. at the location. (Photo: VNA)

Co Loa stretches across the three communes of Dong Anh, namely Co Loa, Viet Hung and Duc Tu. It covers a very large site and is a dominant presence in the northern flood plain of the Red River Delta, so building it would have required a large amount of labour and resources.

Various relics of the Bronze Age Dong Son culture were found at the site. With its unique historical, architectural and archeological value, the citadel has been recognised as a national relic since 1962 and as special national relic since 2012. It is also named among 21 national tourist sites in Vietnam. (Photo: VNA) 

Cao Lo Temple, one of many historical relics inside Co Loa Citadel Complex, is dedicated to an excellent general under the dynasty of King An Duong Vuong who invented a multiple-shot crossbow. A statue of Cao Lo general with crossbows was erected in the middle of the lake in front of the temple.

There is also Co Loa Communal House, an upper shrine dedicated to King An Duong Vuong, and another to Princess My Chau. An Duong Vuong Temple is the most attractive place to visitors. Located on an old hill that once situated the king’s palace, the temple was built in 1687 under the dynasty of King Le Hi Tong and restored in 1893. (Photo: VNA)

An ancient well inside Co Loa Citadel. (Photo: VNA)