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

An echo chamber with a waterfall wrapped around its base at the Embassy of Canada in Washington, D.C.

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

A derelict bit of transportation infrastructure hidden in the woods.

The early data processor factory founded in Washington for the 1890 U.S. Census went on to become IBM.

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

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

There's an old indoor swimming pool hidden directly underneath the White House Press Briefing Room.

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

The first presidential bomb shelter was located in an old vault under the Treasury, connected to the White House via tunnel.

Where the U.S. government kept its actual treasure, before Fort Knox.

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

This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

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

A wondrous old library overlooking the nation's capital.

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

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

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.

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

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

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

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

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