Back when it opened in 1829, a visit to this medieval fortress-looking prison was no fun at all. These days, however, an audio-guided stroll through Eastern State's beautifully decrepit halls is creepily entertaining. The site, in the Fairmount section of the city, is north of Center City West, a few blocks east of the Philadelphia Museum of Art. An hour-long tour provides a glimpse into solitary confinement "rehabilitation" cells (some in use until 1971). There are voyeuristically riveting tales of famous residents -- robber Willie Sutton and superstar gangster Al Capone stayed here -- thwarted escapes, romance behind bars, and incarcerated canines. And then there are the ghosts, who receive extra attention 5 weeks before Halloween. Terror Behind the Walls haunted tours require advanced tickets ($20-$30 each), and take place after dark (Mon-Thurs 7-10pm; Fri and Sun 7-11pm; Sat 7pm-midnight).