Toronto's maybe my favorite city I've ever visited.
My wife and I had an absolute blast just walking around the downtown area (mostly the west streets, as you'll figure out on their grid). We also loved Kensington Market, Chinatown, Greektown and the Beaches neighborhood. I'm pretty sure Queen Street West was their hipster pocket. It's also home to The Rivoli which is one of the centers of their alternative comedy scene and where the Kids In The Hall got their start. We paid an homage and went there.
We just pretty much ate a ton of food, went to a Blue Jays game and popped into a few record stores and things like that. The people there couldn't be friendlier -- we had about four separate people buy us drinks and tell us where to go and would walk with us to places.
I didn't see any shows there but there's a ton of venues and small bars with places. I stood outside a bar in Kensington Market and watched these 50-ish punk rock guys do a mix of old material and a ton of 70s punk stuff. And then a block away were these two girls in their late teens doing acoustic Pixies songs. I usually just walk past street musicians but they were pretty incredible and worth watching for a while.
I think the best way to experience Toronto is to just get a general sense of where
I would seriously move to Toronto if it wasn't in another country and really cold.
