The Hanoi Flag Tower (Cot Co Ha Noi) was built in 1812 during the Nguyen dynasty, as part of the Hanoi Citadel's southern fortifications. It stands 41 metres tall and is one of the most recognizable structures in the city — a three-tiered hexagonal base rising to an octagonal shaft topped by a flagpole that has flown the Vietnamese flag continuously since 1945. The tower is visible from several directions through the surrounding streets and from the grounds of the Vietnam Military History Museum next door.
The flag tower is part of the military museum compound on Dien Bien Phu Street and is typically visited alongside the museum, whose outdoor grounds are filled with captured American aircraft, tanks, and artillery from the wars with France and the United States. The tower itself cannot be entered, but you can walk its perimeter and appreciate the Nguyen-dynasty masonry. The surrounding museum complex has one of the better outdoor collections of war equipment in the country — the F-111 and B-52 fuselage sections are particularly striking in context, given that intact counterparts crashed into neighborhoods a few kilometres away.