Holmesburg Prison was opened in 1896 to relieve overcrowding at Philadelphia’s Moyamensing Prison and was closed in 1995, though portions of the campus are still sporadically used for prisoner overflow, training, and work programs. It was designed based on the same layout as Eastern State Penitentiary and shares many similarities, including cell blocks radiating out like spokes from a central hub.

While most prisons don’t have cheery histories, Holmesburg was regarded as the worst in Philadelphia and with a history of bloody riots, torture of inmates, and the murder of a warden by a prisoner, it easily earned the nickname ‘the Terrordome’. One of Holmesburg’s darkest secrets was the unethical medical testing done on prisoners, however. It is reported that as many as nine tenths of the prison population underwent these studies during the period they were conducted from 1951 to 1974. The experiments ended in congressional hearings, public outcry, and lawsuits alleging the tests were a breach of the Nuremburg Code. The records were destroyed and the lawsuits dismissed, but led to strict regulations regarding the use of prisoners in medical studies.

Holmesburg sits mostly vacant and inaccessible to the public today, although it’s hard to miss it as you go by: it’s the foreboding stone fortress sitting just off of I-95 as you drive by Torresdale. The administration building in front is still staffed and there are usually correctional officers training inside, so it’s best not to try to sneak in!