Based on

Movies like Secrets beneath the streets with Derrick Pitts (2001)

"The subterranean world of the Delaware Valley is a treasure trove of history and a hub of activity 24 hours a day. Historical photos and films set up the stories of these and other mysterious places, but the crux of the program consists of our cameras underground exploring these sites ourselves. Secrets Beneath the Streets takes viewers to places that are just under their feet, but scarcely imagined by the people who walk over them."--Container.