This taxidermy horse was a Civil War hero.

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

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

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

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

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

A derelict bit of transportation infrastructure hidden in the woods.

A wondrous old library overlooking the nation's capital.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

The United States Capitol's former columns still stand.

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

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

The U.S. government built the million-pound stack of steel during the Space Race.

The wooded estate of the Forest Service employee responsible for D.C.’s cherry blossom trees.

Tiny observatory made big contributions to the study of the Earth's motion.

The final resting place of the tragic king and queen of the Jazz Age is tucked away in a small Maryland graveyard.