The legendary building that needed ghostly approval before being built.

A visionary, futuristic sculpture in Los Angeles that never met its extraterrestrial potential.

A haunting tribute to pioneering photographer Clover Adams.

This forgotten boat elevator was an engineering marvel in its heyday.

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

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

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

A Spiritualist house of worship where believers communicate with the dead in the spirit world.

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

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

People escaping slavery may have hidden inside a corpse vault.

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

Before Nixon, "watergate" meant canals.

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

A portal into the bricked up canal that runs through the heart of Washington D.C.

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

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

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

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.

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

There’s a hidden military meme engraved on the World War II Memorial.

This grand gothic brewery has been pumping out suds for over a hundred years.