This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

A hidden passageway now marks the site of an assassination attempt on Ronald Reagan that some say broke a 140-year-old curse.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

An overlooked memorial honoring the local Washington residents who died in World War I.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

100 years later, they're still down there.

Look closely and you’ll notice that the color changes a third of the way up the tower.

A historic arena where the Beatles played their first concert in the U.S.

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

Decades before the scandal, this staircase on the river was a literal "water gate."

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

The house where John Wilkes Booth conspired with his co-conspirators.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

There’s a hidden military meme engraved on the World War II Memorial.

The site of the climactic scene from the classic horror film is now a historic landmark.

The National Park Service’s best-kept secret with views that rival any in D.C.

A once-booming Mississippi River town with a history of racial violence is now eerie and mostly abandoned.

A collection of outdoor art by renowned muralist Robert Dafford depicts the history of a flooded city.

The ancient latrines of the Greeks, in all their public glory.

The alleged house of the Virgin Mary is tucked away in a park and nature preserve on Mt. Koressos in Turkey and is holy to both Catholics and Muslims alike.

The best-preserved ancient theater in the world.

The "Seinfeld" diner.