The last of Philadelphia's wood-paved streets is now a landmark of terrible engineering.

An abandoned railroad tunnel transformed into a creepy path for hikers and cyclists.

Don't get it twisted: This is the oldest pretzel bakery in the United States.

Step into a pastel time capsule where candy is truly dandy.

The oldest active church in Pennsylvania is also the second oldest Swedish Church in the United States.

Penn State's giant bug collection.

One of the oldest log cabins in America is one of the last of its kind this historic Swedish dwelling remains a piece of living history.

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

Contrary to what one might expect, ice forms inside this small cavern during the summer and melts during the winter.

Locals call this magical moss-covered walkway the "Emerald Path."

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

These disused steel furnaces are now haunting ruins that may one day be a national park.

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

This Philly landmark has a giant butterfly pavilion, three floors of insect displays, and withstood a $40,000 heist.

A historic covered bridge is but one example of an oddly prevalent American urban legend.

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

This church in Pittsburgh is home to the largest collection of religious relics in North America.

Mutant vegetables, transgenic mosquitos, and atomic rodents span the walls of this one-of-a-kind museum.

One of the steepest streets in the United States makes an intriguing challenge for cyclists.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

A rare view of a preserved Victorian science museum.

In the bowels of a 19th-century brewery lurks a fine-dining restaurant offering an array of themed feasts.

A restored Pittsburgh house of God has been converted to a marvelous house of suds.

A toxic ghost town sitting atop a massive coal fire.