Season 17, Episode 7 Secret Underground
First Aired: December 10, 2010
Secret underground places are explored, including military installations; and scientific facilities.
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- Premiered: December 10, 1993
- Rating: TV-PG
- Premise: Architectural and engineering landmarks of the 19th and 20th centuries. The programs previously aired on A&E's `Time Machine' series. Among the subjects: the Brooklyn Bridge, the Maginot Line, the Erie Canal, the Aswan Dam and the Trans-Siberian Railroad. (more)