Long time ago, in the 12-14th centuries or so, there were palaces where kings lived. Then the French occupied and built French-style buildings. After that they were home to the Ministry of Defense. Civilians were not allowed to enter. Now the Ministry was relocated to somewhere else and people can go to visit some relics such as steps with decoration of dragons, wells, drainage systems, foundations and walls of old palaces. In some buildings built by French we can see meeting rooms with the chairs specifically seated by famous Vietnamese generals during the war with the American. Even a tunnel for them to avoid bombs.
I really feel satisfied with the visit. I know some more about the history. The citadel is not too crowded, clean, well-organised, with so many trees and plants and paved pathways and some rooms displaying antique objects are even air-conditioned, which makes me feel so comfortable.