Wow, I've never heard Montreal as an answer before. Toronto is the usual one.
Nope, Ottawa, which is about four hours' drive north of Toronto and right on the border between Quebec and Ontario (across the river is Hull in Quebec which is a) the ugliest city ever excluding the museum of civilization and b) will probably, in 50 or so years, become the entertainment side of the city), is the capital of Canada. Toronto was considered to vulnerable because it's so close to the U.S. And Montreal is in Quebec and it was Queen Victoria who decided where to put the capital.
To be frank.
Ottawa's not so large as Toronto (even including all the amalgamated suburbs it's still only a million people). However, Ottawa has the parliament buildings on top of this awesome cliff/hill over looking the Ottawa River which puts it in a very majestic position because everything slopes up to the parliament buildings. It's very nice to walk around on Canada Day
.