This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

The ghostly remains of what was once the world's richest copper mine.

Upside-down trees serve as natural flower pots in this hanging garden of Alaska.

Gorgeous cave resemble a winter wonderland.

Breathtakingly blue walls shimmer inside the "Glacier Behind the Town."

Mind-blowing carvings and fantasy ice scenes grace the largest year-round ice environment in the world.

This whimsical stacked cabin looks like something out of a children's book.

The king of U.S. high points towers over every other peak on the continent.

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

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.

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

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

Philadelphia boasts one of the best — and most often overlooked — traditional Japanese gardens in North America.

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

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

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

A layered tribute to the work of mosaicist Isaiah Zagar.

A rare view of a preserved Victorian science museum.

Mysterious rocks that ring musically when struck.

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

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

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

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

Delicate Wurlitzers, creepy clowns, and The Noid all share space in this insane explosion of kitsch history.