New York's first subway

If noticed this sign in the Subway, you might have wondered what it is. The Pneumatic subway was developed in 1870 by Alfred Beach, preceding the first electric subway system by thirty years.

This system was just a demonstration: The single car was propelled by air. It operated for three years under Warren Street with a station at Broadway. Unlike the never-ending project to build the Second Avenue line, it took only 58 days to construct and it was built in secret in order to avoid paying kickbacks to Tammany Hall politicians.

Turns out this isn't the only abandoned transit project in New York. There are dozens of abandoned lines, unused and unfinished stations, according to people who keep track of this sort of thing.

If you're wondering what it might have been like to ride the Pneumatic Subway, you're in luck—someone's actually made an animation to simulate the ride.