This is one of the highlights of Pittsburgh, along with Frick Park. The GAP trail is a great way to get around (truly, around) the city, and outwards for as far as you want to bike. The trails are safe and there's a really interesting view of the city, especially between the Waterfront and Boston, PA. You can even see parts of Kennywood Park from the GAP trail, and the steel mills in Braddock. You will also pass a good bit of industrial and warehouse waste, which is interesting to see. The rivers are polluted, so it's best not to swim, but the landscape becomes very beautiful around Boston, PA and onward.