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

Washington's iconic carousel has a nice piece of Civil Rights history.

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

This restaurant has been a haven for D.C.'s LGBTQ community since the 1950s.

The most accurate timepiece in the world.

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.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

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

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

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

Largest Roman Catholic church in North America.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

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

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

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

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

The United States Capitol's former columns still stand.

Remnants of a storybook amusement park hidden behind a strip mall.