On Dien Bien Phu street stands the Hanoi Flag Tower, one of the rare architectural works in Hanoi that was fortunate enough not to be destroyed by the French colonialists between 1894 and 1897. It is one of the symbols of the capital.

It was built in 1812 in a prism shape and is composed of three platforms and a tower built with three layers made of baked bricks. It was used by the French troops as an observation tower and communication station between the command headquarters and adjacent military posts.

The first storey is 42.5 m wide and 3.1 m high. Access to the first storey is through two brick stairs. The second storey is 27 m wide and 3.7 m high, with four doors. The eastern door bears the two characters Nghenh Huc (reception of the morning sunlight), the western door bears the two characters Hoi Quang (reflected light), and the southern door bears the characters Huong Minh (towards the light). There is nothing written on the northern door. The third storey is 12.8 m wide and 5.1 m high. Access is through a stair reaching a northern door.

There is a tower upon the third storey. The tower is a truncated octagonal pyramid, 2 m wide and 18.2 m high. A 54 step helicoidal stair is built inside the tower. The stair is lit and aired by 45 openings placed in groups of four or five all along the tower.

And there is eventually a small tower over the tower. The upper tower is octagonal, 3.3 m high, with one window in each side. On the top of the tower, in the middle, there is a cylindrical column, 0.4 m in diameter, used to attach the flag, whose pole is 8 m high.

Therefore, the height of the tower is 33.4 m and more than 41 m if the flag pole is counted.

The success of the August 1945 Revolution resulted in the establishment of the Democratic Republic of Vietnam, and since then, the Red Flag with a Yellow Star has flown over the tower. From here, there are unbeatable panoramic views of the city.