The Pennypack Trail starts at the end of Pennypack Road in Huntingdon Valley, PA.  Continue straight till you join up with the main gravel trail and turn right.  Follow the main trial all the way across the city of Philadelphia to the Delaware River.  The very last portion is fenced off because of the Correctional Facility, so you can't actually get to the river on the trail.  Turn around and complete the run back where you started. 

The path is all double-track and mostly grass. If you find yourself on a skinny single-track trail you are not on the main trail. The route follows pretty close to the lake until the northwest part but later comes back close to the lake when the trail ends and the road begins. follow the road out of the park, over the bridge, and back into the park then go up to the bait shop and veer left into the campground, and follow the roads headed straight south until you find a short gravel road that leads to a gazebo.