Eastern State Penitentiary is considered one of the world’s most haunted places.

A former U.S. prison has been called “one of the most haunted locations in the world.” 
Eastern State Penitentiary in Philadelphia opened in 1829 and tried to reform criminals through isolation which included being hooded in general areas. 
The system of strict solitary confinement gradually ended, in part, due to its questionable impact on inmates’ mental health, but punishment methods were still harsh. 
According to the Travel Channel, “inmates were dunked in a bath of ice cold water and then hung from a wall for the night...” 
Some were tied so tightly to a chair that they later required amputations while others suffered ripped tongues from an iron gag. 
As a result, some say, there have been reports of supernatural activity. 
An NPR report states, “Cellblock 12 is known for echoing voices and cackling; Cellblock 6 for shadowy figures darting along the walls; Cellblock 4 for visions of ghostly faces. Many people have reported seeing a silhouette of a guard in one of the towers.” 
The penitentiary was closed to prisoners in 1971, but it is currently open for tours year-round and offers a special haunted house experience during the Halloween season.