Dr Barnes' $25 billion private collection of art and arboretum.

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

One artist's love letter to his city and its citizens plays out across dozens of bright murals painted on the sides of decrepit buildings.

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

A modern ghost town whose inhabitants were driven away by the growth of nuclear power.

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

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

"Dark Sky Park" is heaven on Earth for astronomers, one of the rare U.S. locations with no artificial light pollution.

Eccentric concrete mansion and museum designed and built by hand from the inside out.

House of vintage taxidermy and Steampunk sculptures in a quiet Pittsburgh neighborhood.

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

Found art has transformed this Pittsburgh neighborhood into a psychedelic dream.

Where America's first doomsday cult awaited the end of the world.

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

A rare view of a preserved Victorian science museum.

A layered tribute to the work of mosaicist Isaiah Zagar.

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

World's first "penitentiary," meant to be humane, drove men insane.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.