It was once the base for a series of domestic terror attacks.

Largest Roman Catholic church in North America.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

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

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

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

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

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

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

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

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

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

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

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

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

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."

An amazing example of early-20th-century architecture, this church features marble transported from Utah.

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

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

When it comes to handsignals (and colonialism) rock always beats scissors.

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

A tiny piece of the Moon is embedded in this stained glass masterpiece.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.