The history (like the thousand year old Temple of Literature)
The interesting if slightly run down French colonial architecture
Government buildings with hammer and sickle symbols (they obviously didn't get the "Communism is dead" memo) and all painted the same colour (which I've dubbed "Socialist Republic of Vietnam Yellow")
Motorcycles everywhere (and my very cute wife)
Young couples "parking" by one of of Hanoi's many lakes, cuddled up on the seat of a 125cc Yamaha which is truly a sight to behold (wish I'd got a picture of that but I didn't want to invade their "privacy")
...the absence of McDonald's or KFC. Don't get me wrong - I'm not one of those misguided types who are opposed to McDonalds or KFC as symbols of American imperialism or some other politically correct nonsense. It was just my shorthand way of saying "I'm glad I went before it ended up like everywhere else."
Just in time it seems.