Eastern State Penitentiary
This place is awesome and creepy. In it's time, this "Hub & Spoke" model prison was a feat of engineering and ingeuity. It had running water and electricity before the White House. It held Al Capone, "Slick" Willie Sutton and Pep the cat-murdering dog.
Today, it is abandoned and a ghost-like relic of the past. At halloween it is a world-reknowned destination for a haunting experience. I will definitely be visiting again!