Eastern State Penitentiary central observation hub

Eastern State Penitentiary, opened in 1829, was built with a radial 'hub-and-spoke' layout that centralized observation in a raised hub and adjacent guard posts. From that central surveillance point guards could observe multiple cellblocks radiating outward, a design that became influential in 19th‑century prison architecture and is associated with the Pennsylvania system of solitary confinement. The historic guard tower and hub remain preserved as part of the site's museum interpretation of prison surveillance.