This mouldering abandoned mental hospital was once a center for progressive healing.

The remains of a failed subway in upstate New York is now an underground graffiti bunker.

This abandoned subway station can still be seen on regular commuter trips.

Tucked away amidst some of the most famous addresses in the world is New York's only fraction of a street.

The famous facade of Grand Central Terminal hides a regulation tennis court, and it's not the first one.

Hidden in one of New York's oldest subway stations is the final remnant of the site of the bizarre Shakespeare Riots.

A controversial magical figure is hidden within a diorama of the city.

Abandoned 19th century homes once occupied by naval officers, soon to be demolished.

A massive forgotten storehouse from 1913 on the Brooklyn Waterfront has a spectacular view of Brooklyn.

The most unloved grain elevator in Brooklyn was a “Magnificent Mistake.”

A grave surprise in the downtown area of New England's second-largest city.

One of the few remaining examples of 19th-century London’s attempt to clean up its reputation.

Hidden inside one of the world's most well-visited zoos is a secret plaque promising eternal life.

This riverfront statue honors the inventor of the first video games ever sold.

The fictional star of "Breaking Bad" is memorialized with a real-life gravestone in his hometown.

These whimsical works of art tell the story of the city's past and present.

A three-piece musical sculpture installed between the subway tracks at Kendall Station near MIT.

A small graveyard is hidden in the midst of a bustling university campus.

These century-old townhouses contain some of the first car garages built in the United States.

This long-hidden space above Westminster Abbey now displays the battle gear of the legendary King Henry V.

This preserved wilderness hides the remains of a colonial grain mill used to feed George Washington's troops.

The innocent intentions of this monument are somewhat lost in the sculpture's muscled imagery.

One of the most dazzling dioramas at the American Museum of Natural History is also one of the oldest.

This taxidermy scene brings the struggle for survival in the Indian jungle to a quiet corner of a Manhattan museum.