Literal "money laundering."

The system of air guns are fired off remotely to scare any trespassing avians.

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

The monumental home of Prussia’s eccentric "Cannon King."

A historic custom house with ties to George Washington is now a shrine to local nautical history.

There’s a secret bunker inside the Brooklyn Bridge, but the city won’t say where.

The origin of the Nixon tapes is rooted in technological incompetence as much as secrecy.

NYC's legendary underground network for bovine transportation.

The pits used to load the nuclear bombs onto the aircraft that dropped them over Hiroshima and Nagasaki at the end of World War II.

In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

Four ionic columns from the Treasury Department building ended up in a park in Nebraska.

About 80% of all U.S. avocados are descendants of Rudolph Hass's glorious tree.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.