Eastern State Penitentiary - pioneering solitary‑confinement prison design

Opened in 1829 and designed by John Haviland, Eastern State Penitentiary introduced a radial cellblock layout and enforced solitary confinement as part of the 'Pennsylvania System' of prison reform. Its architecture and regime were highly influential on prison construction worldwide during the 19th century. The prison later housed notorious inmates such as Al Capone before closing as an active penitentiary in 1971 and now operates as a museum.