A former major munitions plant that has been converted into a sprawling art space.

This lush forest valley was once mined for lumber to the extent that it was once nicknamed "The Pennsylvania Desert."

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.

The one-time stronghold of the noble Douglas family, now home to ghost sightings and nesting birds.

Home to items never before seen by the public.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

A geological mystery on Camelback Mountain.

One of the few guarded stops along the great spice route.

A "miracle" that seems to produce more holy fistfights than holy revelations.

A massive, heart-shaped, wind-carved crater in the middle of the Israeli desert.

A surviving remnant of the thick ice mass that once mantled most of Western Canada's mountains.

Few other hotels can rival the grandeur of the Castle in the Rockies.

Hoodoos, naturally eroded land formations, stand 20 feet tall in the Canadian badlands.

Soaring over the Niagara Whirlpool since 1916.

A church that bred legends, and served as an inspiration for the Da Vinci Code.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

San Francisco's oldest surviving monument and meeting place for 1906 survivors.

Furniture tries to escape an abandoned building in San Francisco.

Where commuters walk through remnants of an ancient Greek necropolis.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

A theatre built to house the rowdy Oxford graduation ceremonies became the stage for a debate about God's existence.

Scattered throughout London are ancient remnants of the city's former bounding wall.