It was hard for me to come to grips with the idea that Ottawa is the capital of Canada: It feels more like the capital of one of the less populous American states. The downtown area is very clean in comparison with U.S. cities of similar size, and the provisions for what we here would call "alternative transportation" (bicycles, buses, etc.) put to shame any U.S. city I've seen.
The architecture of Ottawa's downtown is a strange mix of striking old Gothic-style buildings and rather depressing apartment blocks that can best be described as Soviet-style.
Ottawa has a very cosmopolitan feel, at least to a small-town boy from the Pacific Northwest: Part of it is certainly the bilinguialism. (I remember sitting in a restaurant and being amazed by the conversation at the next table being carried on in at least three langauges, with the occasional intrusion of an Americanism like "get real!" popping up in the middle of a flow of French.)
One aspect of the city that took some getting used to was the traffic: While it's very light, even by the standards of Portland, Oregon, it's very chaotic. This came as quite a shock after spending an entire day in a long and stressful series of airline connections across three time zones. Driving in Ottawa reminded me of everything I've heard about driving in Europe... go, go, go and get away with whatever you can. However, I found that Ottawans were very polite and careful drivers, despite the fact that they seem to feel that turn signals are for turning and have nothing to do with changing lanes. Also, the most overhead clearance I personally observed in a parking structure was 6'4" -- rather cozy.