Obscure Freemasons still live in D.C.’s largest private residence.

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

This sun-scorched lakebed contains samples of half the natural elements known to humankind.

Proto-CIA agents trained with grenades in the sand traps and fired machine guns from the fairways.

Florida’s half-sized replica of the Vietnam Veterans Wall.

This forgotten boat elevator was an engineering marvel in its heyday.

The vertical-axis windmills of ancient Persia have been grinding flour for 1,000 years and counting.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

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

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

The largest radio telescope in the world searches for extraterrestrial life from the remote limestone peaks of southern China.

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

Please don’t anchor your boat onto the Department of Defense’s underwater data cables.

A diminutive plaque recalls the treetop sniper who almost killed Abe Lincoln.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

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

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

A mammoth pair of Civil War artillery guns abandoned out in the forest.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

A fantastic array of trays and cables once whisked books over to the Capitol at 600 feet per minute.

An ear-piercing buzzer calls lawmakers to a vote with a series of long and short rings to form coded messages.

This massive swimming pool is the high tech home to the human-powered submarine races.

The early data processor factory founded in Washington for the 1890 U.S. Census went on to become IBM.

This suburban house is made of dirt, and almost sparked a revolution in home construction.