Imperial Citadel
I have been to Hue’s Imperial Citadel and I would say that the one in Hue is more interesting than the one in Hanoi because it has a larger area and more buildings and structures left. Also because we had a tour guide then to explain to us the history, which gave life to the buildings and structures.
Ho Chi Minh Mausoleum
The Mausoleum was closed for the day due to the holiday so we were not able to get in. We were just content in taking the photos of the seemingly non-breathing military honor guards. And the grounds in front of the Mausoleum is so vast you can play a football game.
One-Pillar Pagoda
When we were looking for this, we were imagining a really big one that can be seen from afar. We had already some assumptions and so every pagoda-looking building we saw, we thought that it could be the One-Pillar Pagoda. But I guess, we thought too much. Apparently, the pagoda is inside a compound with a neighboring museum, both are also to the left of the Ho Chi Minh Musoleum grounds, and it stands in the middle of a small lotus pond.
I can say it is very possible to go around the major parts of Hanoi in a day but add another day for shopping and food explorations (especially the famous Pho, which I believe originated here in Hanoi).