This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

These ancient sunken lanes were naturally tunneled into the soft ground by countless footsteps.

This giant wooden treehouse within a sprawling garden has its own eatery.

Rent out a glass igloo to watch the Northern Lights like you live in the future.

Nuclear waste experts study this prehistoric crater lake to envision landscapes one million years in the future.

Architecturally stunning library serves as the hub of Finnish scholarly life and culture.

This massive library holds what was once the largest book collection in the world.

The oldest stone house in Paris was built by its most famous alchemist.

France's most famous cemetery, with some of its most curious tombs.

The celebrated eyesore created by starry-eyed sweethearts.

The narrowest street in Paris.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Crumbling crypts and overgrown graves rise just out of arm's reach in this forgotten Buenos Aires graveyard.

A neo-Gothic castle in the Argentinian countryside.

A 16th-century horror show built in a lovely Italian garden.