This huge, disused viaduct is now a crumbling concrete underworld of covered in years of graffiti.

The internal railway of one of the biggest steel plants in America has been transformed into a linear park with unique industrial views.

This semi-spooky remnant of an abandoned hotel provides fantastic views.

One of the first commercially successful anthracite-powered iron-making operations in North America.

Sail through this subterranean show cave that is home to a legend that would go on to name nearly everything around it.

These beautiful ruins deep in the Pennsylvania woods are thought to have been a ski lodge or a speakeasy, but no one really knows.

Visitors to Salt Springs State Park are encouraged to literally put their two cents in Penny Rock.

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

A field of nothing but boulders which resembles a giant's gravel driveway.

This eerily well-preserved coal town was saved from destruction by a Sean Connery movie.

The only geyser in the state of Pennsylvania is caused by pressure from an abandoned coal mine outside of the ghost town Centralia.

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

The graffitied ruins stand hidden within the Pennsylvania woods.

Buildings that dynamite couldn't bring down were abandoned because of bathroom issues.

Over 100 concrete munitions bunkers are all that remain of a Pennsylvanian village seized by the US government.

A retired firefighter created this contraption so he and his family wouldn't die if accidentally buried alive.

This permanent exhibition celebrates the finest of our heartless automatons both real and fictional.

It may appear to be a fancy junk yard, but each item has a story to tell and a lesson to impart.

A retrofuturistic art installation in the Pittsburgh Airport.

The house that Frank Lloyd Wright "(shook) out of his sleeve at will" at the age of 86.

A miniature golf course crafted inside the world's largest simulated cave.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

Despite its lavish ornamentation, and wholesome lifestyle of its devotees, this mountain commune has faced its share of issues.

Rows of 19th-century brick ovens used to process coal into coke form the center of a wooded park.