The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

Abandoned concert venue legendary for its rock counterculture.

Terrifying derelict military hospital once housed a recuperating Hitler.

The ruins of an ancient island city built atop a coral reef in the South Pacific are spectacular and strange enough to have inspired H.P. Lovecraft.

A museum of alchemy and a basement laboratory all housed in an ancient building in a Gothic tower.

Bridge that died in war and was resurected.

An abandoned quicksilver mining town surrounded by the Big Bend parks.

Shop selling 500 flavors of soda has something for everyone.

A sacred lake with thousands of sacred carp and a biblical history.

Caves famous for the dragon-slaying saint who lived there.

A nearly unconquerable island-fort in the Indian Ocean.

The curiosities and wonders of pharmacy in a delightful historic building.

Art Deco urban decay at this historical building.

A battle between nature and architecture in the Cambodian jungle.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

An underground mansion with fruit-bearing trees and grapes growing beneath the surface of central California.

A castle hand-built by a Spanish dreamer in the Australian tropical jungle.

Meet the world's longest tapeworm in a collection that really gets under your skin.

A walk through the historic city center, under the streets of Seattle.

Once the most densely populated place in the world, this island is now a ghost town.

The enigmatic and seldom visited ruins of a Mayan city-state.

Venice's island of the dead.

An explosion of natural color known as "the river that ran away from paradise."

One of the world's largest collections of pathological specimens.