Just off the Manayunk Tow Path is a scary haunted house. Intrepid explorers may prefer the northwest side entrance for maximum fright factor. The more direct entrance is up the steps from the path.
Bring flashlights and friends. While you're not likely to find anything more dangerous than some high school kids hidden behind a cloud of pungent smoke, you don't want to do this alone.
Families with kids aged 5 to 12 should make them wait outside until you're confident they won't run loose and hurt themselves. The terrain demands discipline.
To get to the path from I-76, take the Manayunk exit to Umbria then Shawmont. The "Road Closed" sign means you've already entered your very own horror movie... enjoy.