Oh yes, this place brings back memories. Parc Jean-Drapeau is located on a beautiful little island on the St Lawrence River. You can get here using the metro or over the bridge.
The thing I like most about Parc Jean-Drapeau is that it's one of the best running routes I've ever went on (and I've been to a few). The run there and back (to the city) is around a good 15km, but you get to see the beautiful river, the park, and all the industrial stuff on the south side too. I've been on this run several dozen times and I have just touched the surface of its beauty.
Right next to the park is a race track. I haven't been there for any racing events, but I heard it get pretty crazy when there's a race.
This is also where they host PikNik Electronic (during the summer). Never been there myself, but I heard it's pretty rad.