An unassuming secret door once led to a legendary watering hole.

Fake subway tiles were installed to cover a design that resembled the Confederate flag—it's unclear if the resemblance was intentional.

A commemorative plaque hides a door that leads down to the New York Public Library's underground book bunker.

The former home of the reclusive "Weird Wendels" who dominated New York real estate a century before Donald Trump.

Commemorating the spot where the famous scientist fed his pigeons.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

Magnificent New Deal Murals evoke a time when New York City harbor was one of the world's greatest and busiest ports.

This lovely little pond is named after the hundreds of soldiers' corpses that were rolled into the waters during the French-Indian War.

Of all the unique artifacts inside this library, a mummified hand stands out among the others.

A mysterious echo seems to defy the laws of acoustics.

A strangely angled West Village home is the only monument to an explosion that took the lives of three American revolutionaries.

The name of this famed hospital was once a byword for the horrors of medical and psychiatric care.

This castle-like building in Manhattan helped destigmatize cancer in the 19th century.

There are owls with glowing eyes in Herald Square.

An exotic wildlife habitat right off The Strip.

Formerly the world's largest, this Willy Wonka-esque contraption runs 24/7.

These banned cigarette vending machines now sell little pieces of pocket-sized art.

An enormous illuminated figure dances on the Las Vegas strip.

These markers are used to determine the ground stability of the Strip.

Take a dip in the world's largest mineral hot springs pool.

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

Even in death, he's still your huckleberry.

One of the greatest heroes of the Titanic tragedy came from humble beginnings to this beautiful home.

A focal point of in Denver’s skyline for over a century, inspired by a Venetian basilica.