D.C. once had its own tiny rival to the New York Stock Exchange.

A promising candidate for the lost rock laid by George Washington was unearthed, but the hunt is still on.

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

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

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

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

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

They sort through millions of dollars worth of diplomatic gifts on behalf of the government.

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

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

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

Perhaps the most scandalous statue of America's first president.

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

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

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

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

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

The most accurate timepiece in the world.

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

The "lovely red Vega" of the legendary record-settling pilot.

A computer bug so primitive it was an actual insect.