This unusual rock formation looks like an apple that has been neatly sliced in half.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

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

Two stunning 17th-century libraries and a cabinet of curiosities.

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

Eons old volcanic activity created one of the most stunning rock formations in the United States.

This historic stone bridge has an entire neighborhood clinging to its sides.

Towering basalt columns, a creation of fire and ice.

An ancient stone fortress considered by many to be the eighth wonder of the world.

A sharp bend in a dramatic river canyon cut through red rocks.

Tubing through a cave lit with glowworms is a magical underground experience.

Roman ruins top white travertine terraces formed by ancient hot springs.

A solitary tree has grown up all alone on Lake Wānaka, backdropped by the beautiful Southern Alps.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

The highest point in Belgium is a staircase to nowhere.

A moving memorial to the fallen and missing from WWI trenches.

Museum in a swimming pool where the water still flows.

Hiding the longest subterranean river known in the world.

Visitors to this Belgium graveyard are greeted by the grieving stone parents of the young men lost to war.

This collection of lurid religious statues tell the tales of a saint who stood down the devil.

The tiny Belgian town's ancient version of Mardi Gras involves eerie wax masks, sticks for warding off evil, and ostrich plume hats.

Petting this mysterious iron monkey supposedly brings good luck.

The world's tallest boat lift stands as a massive piece of industrial tourism.