The sounds of the world's largest fully functioning pipe organ dazzle shoppers at a Philadelphia Macy's.

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

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

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

This stone tower marks a lookout point over the historic Washington Crossing, and maybe some buried treasure.

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

This Pennsylvania cave holds evidence of the oldest known inhabitants of North America.

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

An indoor miniature village and labor of love for Laurence Geiringer, a model railroad enthusiast.

The first American department store, and home to the largest operating musical instrument in the world.

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

A stone arch leads to a cavernous 1930s spring house tucked away in the Pennsylvania woods.

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

An abandoned stretch of highway, deteriorating next to the operational one.

Hellam Township is reputed to feature seven remote gates, which when passed through in the right order, open an entrance to hell.

Mysterious rocks that ring musically when struck.

An abandoned cemetery lies in ruins as the surrounding forest swallows it whole.

Hundreds of protractors affixed to surfaces all over the city.

There aren't too many operational funiculars around, but Pittsburgh has two!

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

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

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

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

This abandoned school has had many lives since the early 1900s, and all of them doomed.