Pneumatic subway

The pneumatic subway is an abandoned subway system beneath the New York City borough of Manhattan, appearing in the 2012 TV series two-part episode The Manhattan Project. It was secretly being traversed by Kraathatrogons, whose movements kept causing earthquakes in the city above.

Trivia

 * In real life New York City, there was a single pneumatic tunnel constructed for demonstration purposes, called, which was part of a proposal for a wider pneumatic underground rapid transit system that ended up not being built. The future New York City Subway was designed to use rail power instead of pneumatic delivery.  The fictional pneumatic subway appearing in the episode is never specifically identified with this real life version.