I highly recommend coming to this place if you're new to Montreal, visiting of have lived here forever.
Its nice in the summer, relaxing and the view when you get on top of the mountain is fantastic! You see all of downtown Montreal and even more. Try spotting some popular landmarks like "Concordia University" or "Old Montreal" - because you can totally see them from way up there!
The walk up is done through stairs and can become a bit tiring so just bring some water. There is a water fountain at the top, though.
They also sell popsicles and some ice cream when you get to the top
*you can also get to the top by car, but the walk up is nice as it feels like you're in a different place far away from the city, which I enjoy*