The national park was once a plantation estate.

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

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

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

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

Home to items never before seen by the public.

The site of the climactic scene from the classic horror film is now a historic landmark.

The United States Capitol's former columns still stand.

America's smallest national park site is the former residence of exiled Polish national hero Thaddeus Kosciuszko.

The souvenir got the company’s founder out of a pretty pickle at the World’s Fair.

Alexander Hamilton’s creation caused quite a bit of controversy.

This forgotten building was one of the few Philadelphia-area breweries to survive Prohibition.

A planned settlement in Pennsylvania once housed the aristocratic refugees of the French Revolution.

According to local myth this cemetery is half evil spirits, half good—split down the middle.

The residents of the Neighborhood of Make-Believe live without much fanfare within the Pittsburgh Children's Museum.

It would take 35 firetrucks to fill this enormous glacial pothole.

Board a mine car and descend the #190 slope 300 feet underground into the Clark Vein of coal.

This lush forest valley was once mined for lumber to the extent that it was once nicknamed "The Pennsylvania Desert."

This elaborate towering structure was once famed for its revolutionary height.

Ant sculptures march up the side of what used to be an iconic spot in punk rock lore.

Yo, Adrian!

The remains of a community that was forced to move for a dam that never materialized still rot in this Pennsylvania park.