The oldest surviving botanic garden in the United States.

The origin of this mechanical boy was a mystery until he revealed his maker by writing it in perfect cursive.

This little-known collection holds everything from "Dracula" notes, to the manuscript of "Ulysses," to the forged works of Shakespeare.

An abandoned cemetery lies in ruins as the surrounding forest swallows it whole.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

Mountain where Jesus was first tempted by the Devil.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

This cemetery features modernist statues as strange as its name.

This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

Helen Keller once broke ground on this historic center for the study of technologies to benefit the hearing impaired.

When it comes to handsignals (and colonialism) rock always beats scissors.

In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

A brass plaque dedicated to a convicted cannibal hangs in the National Press Club, and that's not even the craziest part of the story.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

This abandoned caretaker's apartment is one of 13 left in the New York Public Library system.

This hidden oasis features a stunning view of the Hudson River and the Palisades from a castle-like museum.

The famous author's cottage hideaway.

A former connection to City Island, it has been abandoned since the 1930s.

The end of the 4 Line is also the end of the line for 300,000 souls in one of NYC's most illustrious cemeteries.

This old estate is a remnant of when the Bronx was a popular summer destination for wealthy New Yorkers.