We chose Hanoi because that's where the tours to Halong Bay leave from and that was the big draw for us to go to northern Vietnam.
Temple of Literature - Vietnam's 1st University
The food was excellent! And cheap. That alone was worth a visit.
Ho Chi Minh's memorial
We didn't get to go in because it was closed but it was one of the things on my list to see and didn't disappoint. We didn't stay much longer than just getting a few pictures. The sun came out from the clouds and it got hot. The sun and humidity just did us in.
Hoa Lo Prison
We didn't do too many historical sites from the Vietnam war. This prison was much older than the Vietnam war, but was nicknamed "Hanoi Hilton" during the war.
The office government buildings were all this lovely cheese color.
Ho Kiem Lake
All things considered, if I ever got back to Vietnam I would go see central and southern parts, or even more northern like Sapa. But Hanoi was ok to visit once.