The site of the little-known Pennsylvania battle that sparked the Seven Years' War.

For decades, it has disappeared and reappeared as water levels rise and fall.

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

Hidden behind West Philadelphia rowhomes is a haven for migratory and local bird species both ordinary and rare.

North America's oldest quarantine facility was built in response to Philadelphia's 1793 yellow fever outbreak.

The world's third-largest crystal sphere has sat in the Penn Museum since 1927 with the exception of one outlandish theft.

Behold the rickety wooden glory of the world's oldest operating roller coaster.

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

Erected in 1697 this Philadelphia bridge is the oldest surviving roadway bridge and perhaps the oldest stone bridge in the United States.

One man's real life disfigurement inspired a lasting local legend surrounding an eerie tunnel.

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

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

This secluded walking trail is a hidden gem of a Pittsburgh park.

The largest university building in the West is a gothic masterpiece containing dozens of theme rooms based on different countries.

When the Austin Dam failed it destroyed much of Austin...and then it failed again.

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

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

A failed piece of Orientalism has become the proud symbol of a community.

A train station that was abandoned by the coal industry and was later converted into a cocktail bar.

A quiet, gothic haven nestled between Pittsburgh's Squirrel Hill and Point Breeze neighborhoods.

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

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

This hidden gem of a garden has one of the only surviving Victorian ferneries in America.

This Old Testament garden features 100 plants from biblical times.