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.

Behind an abandoned storefront is an example of pioneering 1930s gas station architecture.

A hidden passageway now marks the site of an assassination attempt on Ronald Reagan that some say broke a 140-year-old curse.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

Was there a small "backpack nuke" hidden in the attic? JFK apparently thought so.

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

This nine-story building is the oldest standing skyscraper in D.C.

A replica of the famous memorial statue at the Normandy American Cemetery hides in an office building in downtown D.C.

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

This unassuming passageway played a key role in one of the most important events in U.S. history.

Over the last century, this elegant columned facade has been home to the headquarters of a bank, several nightclubs, and a restaurant.

Coins and medals straight from the mint await visitors to this shop in the nation's capital.

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

Go take a picture with the inventor of the daguerreotype photographic process.

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

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

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

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

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

A spectacular tribute to statesman and philanthropist Andrew Mellon.

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

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

The 28,000-year-old specimen is remarkably intact.