Decades before the scandal, this staircase on the river was a literal "water gate."

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

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

Art deco landmark on the outskirts of Washington, D.C.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

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

Largest Roman Catholic church in North America.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

"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 hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

Housing the National Women's Party since 1929, this historic house is now a monument to the fight for gender equality.

A much-maligned monument to teetotalism.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

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

Despite violent work crews and massive delays this abandoned canal tunnel was built to last into the modern day.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Captain John Smith thought these cliffs were amazing in 1608 but sharks thought so 20 million years before him.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

Rediscovered after a century, the father of the American Navy was reinterred in something dredged up from Davy Jones' Locker.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

America's first federal monument.

A super-sized promotional trick that is now a D.C. landmark.

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