Eastern State Penitentiary
From 1871 until 1971, the Eastern State Penitentiary, also known as ESP, was the first prison in the United States to redefine incarceration and emphasize reform rather than administer punishment. The prison's innovative wagon wheel design quickly became a model for prisons worldwide but it did come at a cost, as it also had become the most expensive structure ever erected. Now a U.S. National Historic Landmark, the prison is open to the public as a museum. Tours are also available 7 days a week.