The no-longer-abandoned Eastern State Penitentiary in Philadelphia, PA. Closed in 1970, ESP was left to decay until Eastern State Penitentiary Historic Site Inc. began offering tours to the public in 1994. Now, it's one of the city's major tourist destinations, drawing over 220,000 visitors a year.

Luckily, they were kind enough to let me into some of the areas that are still off limits to the public 😉 https://www.abandonedamerica.us/eastern-state-penitentiary