Through the ups and downs of history, the 5 gates of Thang Long citadel, namely Quan Chuong gate, Cau Giay gate, Cau Den gate, Dong Mac gate, and Cho Dua gate, have always existed in the hearts of Hanoians.
The ancient Thang Long citadel was surrounded by 3 rivers: To Lich river, Red river, and Kim Nguu river. Most of the gates faced these 3 rivers.

According to “Bac Thanh du dia chi” compiled in the early 19th century, Hanoi had 21 gates. However, in 1831, when King Minh Mang established “Tinh Ha Noi”, the “province” area (ie Hanoi’s inner city) was mapped with only 16 gates. By 1866, under King Tu Duc, the map of “Tinh Ha Noi” had only 15 gates…
In the 20th century, with the changes of history, many gates gradually disappeared. Hanoi has only 5 gates that are often mentioned and have become famous places in poetry and literature.
Quan Chuong Gate is the only gate that still retains its old appearance, located on Hang Chieu Street, Dong Xuan Ward, Hoan Kiem District, Hanoi.
The materials used to build Quan Chuong Gate are bricks and stones, quite large in size, similar to the type of bricks used to build the walls at the Temple of Literature.
Quan Chuong Gate was built in the 10th year of Canh Hung (1749) of the Le Dynasty. In the 46th year of Canh Hung (1785), this gate was overhauled. In the 3rd year of Gia Long (1804), it was rebuilt and expanded to its current size.
Cau Giay Gate
Cau Giay Gate Since the 19th century, to facilitate the paper business for sale to people in the inner city, the paper villagers in Yen Hoa have built paper stalls at the gate, commonly called paper bridges. Therefore, the name Thanh Bao Gate is also called Cau Giay Gate. The word "bridge" here means a market bridge, not a bridge across the river.

Cho Dua Gate (Dong Da District) is now the intersection of 6 streets: Xa Dan, Kham Thien, Ton Duc Thang, Tay Son, De La Thanh, and Cho Dua. Cho Dua Gate has more than 760 years of history, formerly a very large gate and one of the important military defense positions in the south of Thang Long Citadel. Near the gate, there is a small market under the shade of coconut trees, which partly explains the familiar name of the gate.

O Cau Den is the intersection connecting the four streets of Hue, Bach Mai, Tran Khat Chan, Dai Co Viet. O Cau Den's Chinese name is Yen Ninh, located behind the ancient Thinh Yen citadel. According to Dai Viet Su Luoc, the place name O Cau Den in Thang Long appeared in the history books of the Ly dynasty, that is, around the 11th-12th century.
According to the story, from ancient times until the years 1945-1954, the current location of O Cau Den had a river flowing through it. On both sides of the bank were alluvial soil with rows of vegetables that flourished all year round, the most abundant of which was amaranth. The bridge across the river was therefore called Cau Den and the name O Cau Den also originated from there.

O Dong Mac is located at the end of Lo Duc street, at the intersection with Tran Khat Chan street and Kim Nguu street. O Dong Mac is located not far from O Cau Den. During the reign of Lord Trinh Sam (18th century), O Dong Mac was called O Ong Mac. The 1831 Hanoi map called this gate O Thanh Lang. In 1866, the map named this gate Lang Yen. In the 20th century, people used to call it O Dong Mac. In the past, this gate was the place to enter Thang Long citadel by both land and water, so it was often guarded by soldiers quite strictly.