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

When the rain falls, this drain system turns into a musical instrument.

This fantastical house shaped like a seashell brings aquatic design to architecture.

A lovers' beach, tucked below the surface of the island, provides a safe haven for romance.

A lake at the bottom of the ocean.

A beautiful geyser under environmental threat.

Rusting ships sit in a desert where a sea used to be.

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

A marvel of Byzantine engineering under the streets of Istanbul.

An ancient capital city that dates back 3,000 years old and harbors many surprises.

Source for a sizable portion of Egypt's freshwater supply is more than an optical illusion.

Fur-lined metal pod dangling in the French countryside.

Bridge that died in war and was resurected.

Northern Ireland's Brobdingnagian stepping stones.

The world's highest and most dangerous infinity pool lies at the precipice of Victoria Falls.

A unique underground structure dating back to the 1st century BC.