When you want to go for a run, walk, or bike ride, the Schuylkill River Trail is a great place to go. The trail doubles as a route for transportation. It's 60 miles (96.5 km) long and goes from Philadelphia to Parkerford and then continues all the way to Auburn, PA (which includes some on-road riding) if you're feeling extra ambitious.
Although many use it as a way to keep fit and active, it's a nice scenic route that you can take to get to other parts of the city if you are looking for an alternative to public transit. Within Philly, the trail goes to the Art Museum, the Zoo, Bartam's Garden, and the well-loved Manayunk neighborhood.
Don't have a bike? No problem! Rent a bike from Indego. They have many stations in the city, a few right by the river. www.rideindego.com/stations