Literal "money laundering."

Depending on who you ask, this controversial treehouse is either a charmingly creative child's playhouse or an illegal encroachment on public land.

The tunnel under the Capitol Building where Congress takes out its trash.

The National Park Service’s best-kept secret with views that rival any in D.C.

D.C. once had its own tiny rival to the New York Stock Exchange.

This grisly headstone doesn’t seem to be resting in peace.

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

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

The walls of the iconic dome are hollow and have a secret stairway.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

A menagerie of concrete animals brought together from across New York City's parks.

The author's beautiful and historic home is also a fully functioning goat farm.

You can find America's highest suspension footbridge at Grandfather Mountain in North Carolina.

A 315-foot spire jutting out from the Blue Ridge Mountains makes for breathtaking views.

Practice your Dirty Dancing lifts in the manmade lake where Johnny Castle himself did.

This granite rock face is named for the magnificent reflection that occurs when the sun hits it just right.

The U.S. Supreme Court's secret Cold War relocation facility in the mountains of North Carolina.

This research center for rare prosimians is studying how they sleep to help prolong human life.

This North Carolina museum is keeping the pinball craze alive, with a little Space Invaders on the side.

A piece of outsider public art accompanied by a strange urban legend.

Gnarled canopies of pink and purple wildflowers arch over the trail to the summit.

Who needs fancy modern water slides when this giant North Carolina rock works just as well?

The highest point in Maryland is only accessible by hiking through another state.

This abandoned amusement park was built on a site with a dark history.