In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

A much-maligned monument to teetotalism.

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

Art deco landmark on the outskirts of Washington, D.C.

A small triangle of DC grass is the final resting place of one of Sonny and Cher's songs.

An unassuming, powerful monument north of the U.S. Capitol bears witness to the resilience of Japanese Americans during a time of grave injustice.

When it opened during the final years of the embargo, all the drinks and cigars were free.

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

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

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

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

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

There's a crumbling old mansion inside the Smithsonian National Zoo.

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

The "lovely red Vega" of the legendary record-settling pilot.

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

Seemingly unremarkable items like empty sushi trays, chef hats, and freshness stickers are being preserved so future generations can look back on this beloved cultural import.

People escaping slavery may have hidden inside a corpse vault.

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

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

A nostalgic bibliographic gem.

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

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

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.