Further to @ReedOnTheGrand's explanations of stadiums. I present another amazing opportunity in KW:
http://www.cbc.ca/news/canada/kitchener-waterloo/schneiders-kitchener-sold-auburn-development-1.4318369
This is probably my favourite option for a site. The site will take years of brownfield development before it can be fully usable for residential and Auburn itself is known for taking awhile to get things going (see the Arrow Lofts and Barrelyards Development). At the back of the site is a railroad track, which also won't be great for residential but perfect for something like a stadium, where a train coming by once and awhile is fine. It's close to downtown and right on the LRT line. It's also close to the Iron Horse trail and a favourite Grand River Union brewery, Together We're Bitter Brewing Co-op.
I think a modular stadium could pop up in this location very quickly. It would be a great way segue for Auburn and fantastic for city access.