This hunter-gatherer architecture is believed to be the oldest religious complex known.

This 16th-century monastery has been turned into a surrealist architecture compound.

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

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

This community on a small Venetian island has taken to painting their houses in bright neon hues.

Houses are tucked between, on, and underneath giant boulders.

Architectureal fantasy quarter of Rome.

France's national museum of scientific and industrial instruments.

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

An abandoned saucer-shaped monument in the Bulgarian mountains.

This attraction was abandoned after the Chernobyl disaster.

Renaissance villa and gardens complete with a tormented colossus.

The most visited, and possibly most controversial, museum in Germany.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

Stalactites and stalagmites in a beautifully lit cave.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

Pompeii's less famous neighbor is still revealing her secrets.

An alchemist's "magic door" stands in the middle of a Roman park.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

Thousands of well-dressed mummies below a monastery.