Hidden in Washington, D.C.

Amid the sprawling Defense Intelligence Agency Headquarters is one of Washington's least accessible museums.

A secret greenspace hides atop a Capitol parking garage.

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

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

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

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

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

People escaping slavery may have hidden inside a corpse vault.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

There's an old indoor swimming pool hidden directly underneath the White House Press Briefing Room.