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

Largest Roman Catholic church in North America.

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

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

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

At 207 feet, one of the world's longest continuous escalators.

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

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

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

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

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

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

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

Home to items never before seen by the public.

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

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

A much-maligned monument to teetotalism.

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

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

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

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

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

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

Look closely and you’ll notice that the color changes a third of the way up the tower.