This is actually a circular French built water tower called the Hang Dau Water Tower. It is located to the north of the Old Quartere and to the northeast of the Citadel. It is said to be the first to supply water for the city but it has not been utilized for the last few decades.

The Hang Dau Water Tower had signs of restoration works and is one of the tourist attractions in Hoan Kiem - Hanoi .