A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

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

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

On the Fourth of July this area will transform into a Pompeii-like storm of falling embers and ash.

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

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

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.

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

Look closely and you’ll notice that the color changes a third of the way up the tower.

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

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

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

Home to items never before seen by the public.

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

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

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

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

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

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

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

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.