This restaurant has been a haven for D.C.'s LGBTQ community since the 1950s.

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

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

A historic arena where the Beatles played their first concert in the U.S.

This church built atop a gas station promises to "equip you for the next stage in your life’s journey."

At 207 feet, one of the world's longest continuous escalators.

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.

Need a hardcopy of the 50-title Code of Federal Regulations? This is the place.

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

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

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

The national park was once a plantation estate.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

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

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

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

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

A much-maligned monument to teetotalism.

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

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

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

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

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