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

The fantastic architectural models of a French traveler.

Historic medieval fortified city in southwest France.

The bizarre home and sculpture garden of an eccentric artist.

The largest underground church in Europe.

A 14th century bridge built as a fortress, where the devil lurks on one of its towers.

Bordered by forest on three sides and the ocean on the other, the Great Dune of Pilat is the highest sand dune in Europe.

Ancient paintings known as the "Sistine Chapel of Cave Art."

It should come as no surprise that the best view of the Hollywood sign is from Batman's lair.

This former boomtown "island" is now submerged below Folsom Lake.

Haunting and beautiful trees, doomed to die.

The ruins of the castle that chemicals built.

One of the most unusual geological features, recognizable from a dozen hit movies.

Colorful and chaotic stacked hotel in North Holland.

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

Each year these high desert hills are absolutely covered with poppy flowers in a surreal show of nature.

Remants of foundations, streets, and streetcar tracks inhabit the cliffs where a landslide occurred in 1929.

Commonly referred to as the most photographed Victorian home in the United States.

California's own medieval Italian castle, authentic down to the 300-year-old iron maiden in the dungeon.

Invisible bridge parts the waters, invoking biblical images and preserving the ominous feel of an ancient moat.

“And the Lord said unto Johan, build for thee an ark for the end of the world is approaching.”

A beautifully eclectic mix of architectural styles.

The world's only museum devoted to the wonders of fluorescence.

Dutch woodpile home in the forest.