I always really liked this submission from that competition a while back. I think the movies at Assiniboine park are pretty popular and I bet movies here in the summer would be too if the space was nice. Having somewhere to store a kayak or canoe for nearby residents would be awesome if it was fairly secure. Of course there should also be space dedicated to MMIW.
This could also act as a stop for a waterbus between the exchange and the forks and beyond. From a tourism perspective, a city-wide waterbus could be pretty great. You could stay at a hotel in the exchange or the forks and travel via boat to destinations like the Leaf, zoo, and Rainbow Stage.