I forgot a lot more stuff about Montreal - Tourists take note!
During our many summer festivals some of the main downtown streets are completely closed to traffic after rush hour and thousands (at times during the Jazz Festival there are 100,000 people at the free street concerts) of people descend on the various locations. Everything is very well organized, lots of medical personnel walking around just in case (it gets really hot in the summer, some people get dizzy, etc.), lots of unobtrusive security people, food stands and free whatever:
if it's the Jazz Festival, there are all kinds of bands playing for free - stages set up all over the place, even an area for kids to play, musicians from everywhere are in town. Then there are the paying venues with people like Diana Krall, Ray Charles, Tito Puentes, etc.
during the World Film Festival there are screenings in just about every theatre, plus huge screens are set up outside the concert hall with free film screenings every evening after 9:00 p.m.
during the Just for Laughs festival there are free skits, comedians, etc. besides the paying venues where Seinfeld or whoever are doing their thing
during the Grand Prix weekend a few streets are closed, music blaring and every Lamborghini and Maserati and Porsche are displayed, plus Rolls Royces (price tags displayed if you're in the market). Paul Newman and such like ones are fairly regular attendees at the Grand Prix.
Besides that there's Old Montreal, with artists doing their bit on the pedestrian-only cobblestone streets, as well as art galleries to stroll through. Cirque du Soleil is usually here once a year, then if it's raining there a whole underground shopping/theatre/restaurant complex which runs for blocks under the downtown core and connects many office buildings with the subway system.
There's also the Botanical Garden, second largest in the world (I believe Kew Gardens in England is the largest), or the Biodome (four different ecosystems represented, i.e. tropical rain forest, the Arctic, where you're nose-to-nose with several varieties of penguins, etc.).
Anyway you get my drift!