One of the best part of my summers is walking, biking, sitting anywhere in Vieux-Montréal.
I make sure to do it at least once every summer and on a perfect day (sunny and warm)
It really just transports you. It's charming and old-timey. It's the quintessential Montréal tourist activity.
You can have a queue de castor while walking down all the beautiful shops, you can head to Vieux Port to see some boats or zipline, you can try out a number of escape the room games, you can see Cirque Du Soleil, you can go to Bota Bota, and etc!
The possibilities are truly endless.