What it is
The tower went up in 1812 under the Nguyen dynasty as part of the Hanoi citadel. It was a watchtower and a signal post.
When the French tore down most of the citadel in the late 19th century, they kept the tower and used it as a military post. That is why it survives almost intact today. It stands just south of the Imperial Citadel of Thang Long, on Dien Bien Phu Street, and it has become one of the city's best-known symbols.
What to look at
Start at the base. Three stacked square terraces, each smaller than the one below, lead up to an octagonal brick tower about 33 meters tall. Look for the small windows that let light into the spiral staircase inside.
Walk all the way around. The thick brick walls and arched gateways show how solidly it was built. Then step back toward the street for the classic photo, with the red flag against the sky. Access to the upper levels can vary, so ask on site whether you can climb.
When to go
Morning is the most pleasant time. The light on the brick is soft and the heat is lower. Late afternoon also works well for photos. On weekends and public holidays expect more local visitors, especially school groups.
Combining it with nearby places
The Imperial Citadel of Thang Long is just across the street. Visit it first, then stop at the tower on your way out. Lenin Park, with its statue, sits directly opposite the tower.
The Fine Arts Museum is about 0.4 km away, and Ba Dinh Square about 0.6 km. The Presidential Palace and Stilt House are around 1 km away. Heading back east, Hang Ma Street in the Old Quarter is also about 1 km away.