This head-spinningly bizarre Depression-era art cave is wall-to-wall quartz and Jesus.

It specializes in outsider art and artifacts of secret societies.

The ruined remains of a coal mining ghost town are hidden within the woods.

Paths are maintained, but trees have taken over plots.

A promising candidate for the lost rock laid by George Washington was unearthed, but the hunt is still on.

100 years later, they're still down there.

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

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

Giftshop catering to cryptozoologists and anyone with a sense of humor.

An astounding collection of medical specimens, including bits of President Lincoln.

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

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

A computer bug so primitive it was an actual insect.

More than 500 unique and specially designed cases collected by D.C.'s "Harmonica Case Man."

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

The first presidential bomb shelter was located in an old vault under the Treasury, connected to the White House via tunnel.

There's an old indoor swimming pool hidden directly underneath the White House Press Briefing Room.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.