The Don Valley River runs through the heart of Toronto. It's about a five minute drive from where I grew up yet I've never walked the trail next to it. It's nice in parts but generally pretty shabby.
It probably wouldn't take much work to make this a nice trail. If the City extended the Riverdale Farm design down through the trail and cleaned up the garbage it could be a beautiful walk. Throw a few container stores like at Dundas and Bathurst along the walk and it could be a bunch of new jobs for Regent Park/St. Jamestown.