See the rare bloom of the "Queen of the Night" cactus at one of the world's largest succulent collections.

One of the only cooperatively owned bars in the nation wears its eclectic history on its walls.

One of the world’s smallest bars, just 13 square feet, is brimming with speakeasy flair.

During Prohibition, the U.S. Congress had an "official" bootlegger, with his own Capitol Hill office.

There’s a special club house at the top for the bell ringers.

The fountains of the U.S. Navy Memorial are annually salted with water from the Seven Seas as part of a nautical ritual.

A building shaped like the Army Corps of Engineers logo, because why not?

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

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.

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

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

Obscure Freemasons still live in D.C.’s largest private residence.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

The oldest continuously operating fish market in the United States.

When it opened during the final years of the embargo, all the drinks and cigars were free.

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

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

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

People escaping slavery may have hidden inside a corpse vault.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

The walls of the iconic dome are hollow and have a secret stairway.

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

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.