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

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

A Gothic cathedral created from volcanic rocks.

Series of underground houses inhabited continuously for centuries.

Historic medieval fortified city in southwest France.

Live-in sculpture begun by one family in 1979.

A French library that makes sure its love of books is writ large... giant in fact.

These quaint French houses dangle precariously over a precipice.

Despite centuries of architectural innovation, this French castle is being built like it's the 13th century.

One architect's organic, human-centric design has been fully realized in this alien art house.

A medieval house adorned with enigmatic carvings, including one of a man displaying his masculine attributes.

These rustic holiday homes are made from discarded fishing boat hulls.

This building’s ghostly exterior reflects its former lives as a prison, school, and funeral home.