The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.

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

An ornate Art Deco tile mosaic representing Nebraskan life, both modern and prehistoric.

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

Hidden for 165 years inside a building designed by Thomas Jefferson are the remains of what may be America's first educational chemistry lab.

Edgar Allan Poe's old dorm is now a shrine to the author's legacy.

The unluckiest U-boat in the entire German fleet is now on display in a Chicago museum.

The twin towers in this Chicago fountain use 50 foot tall video screens to spit on people.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

The oldest working bell set in North America, the bells at Old North Church sat silent for their first four years in Massachusetts.

The massive machine creates cracking displays of indoor lightning.

The site of Paul Revere's historic two lantern warning.

Macabre headstones carved with winged skulls, dancing skeletons, and pithy reminders of impending death.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

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

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

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

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

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

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

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

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

Light bulbs, scrap wood, and tinfoil comprise this homemade throne of the gods.

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