Ontario Place is an 93 acre waterfront park in Toronto. Attractions including Cinesphere (the world’s first permanent IMAX cinema, now in 3D) - a waterpark with a sand beach and a pool right at the water’s edge overlooking Lake Ontario. Last year (2011- 40th anniversary), the entry was free! I have seen many great concerts there in the 70's-80's, when I lived 5 minutes walking distance away.
Ontario Place closed its doors in fall 2011. Its future is still to be decided. It sits on a valuable waterfront property (owned by the province) and upscale condominiums are not ruled out yet.