The hippo that stands on this university campus was once a drunken flea market purchase.

One of the three perfect vellum copies of this historic book known to exist is on display in a specially-designed case.

On the Fourth of July this area will transform into a Pompeii-like storm of falling embers and ash.

The tunnel under the Capitol Building where Congress takes out its trash.

An obscure federal monument honors the French diplomat who served as Ambassador to the U.S. during WWI.

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

This statue of one of baseball’s greatest pitchers looks like something out of a sci-fi horror movie.

The U.S. Navy’s preposterously detailed mini battleship took 77,000 hours to complete.

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

Once a sewer culvert, this road tunnel now offers cyclists and pedestrians a subterranean stroll under the C&O Canal.

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

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

There just so happens to be a court even higher than the U.S Supreme Court: a basketball court in the building itself.

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

Also known as the Founding Church of Scientology.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

100 years later, they're still down there.

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

Where you can hail your favorite fictional commanders-in-chief.

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

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

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

Where the U.S. government kept its actual treasure, before Fort Knox.

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