Lots of great stuff to do in DC. I could spend a week in the Smithsonian alone. I don't think you want to any "Presidential" activities at the moment though. :)
If I go for a four hour walk in Toronto or Montreal people think it is a good idea. If I do it in LA they have never heard of anyone doing that before. In Chicago, outside of the north lake shore, people can't believe I survived. In Phoenix, you actually might not survive.
It is so funny. I have known people in Toronto for 20 years and I have no idea whether they have a car or not. I only found out one of my friends had a car after 3 years when we were going to a cottage and she offered to drive. Turns out that all but a couple have them but never use them in the city. <insert shrug ASCII> Love walking around NYC though. Motorbikes are good enough for Asia. Have never considered renting a car in Europe, although I probably should at some point.