The most accurate timepiece in the world.

Daily lunch spot for many of Washington, D.C.'s cab drivers.

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

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

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

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

People escaping slavery may have hidden inside a corpse vault.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

A line of blue paint marks the route of the inaugural parade.

The bank that helped fund the Mexican-American War and the purchase of Alaska met its downfall after helping Augusto Pinochet launder money.

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

A historic neighborhood church is reborn as a psychedelic arts collective.

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

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

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

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

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

The most decorated dog of World War I is preserved in the Smithsonian.

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

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

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

The innocent intentions of this monument are somewhat lost in the sculpture's muscled imagery.