The world's largest reflecting pool is just two centimeters deep.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

The industrial architecture honors the laborers who brought the Exposition Universelle of 1900 to life.

The fantastic architectural models of a French traveler.

A medieval military street hidden beneath a charming French fishing village.

Avant garde house of Pierre Cardin on the Cote d’Azur.

An aluminum skeleton brings Chinese mythology to the French shore.

This massive blockhead sculpture hides an entire library.

A Gothic cathedral created from volcanic rocks.

A French valley with forests so lush it was nicknamed "the Small Amazonia of the Pyrenees."

The largest underground church in Europe.

A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

An icy lake tucked among jaw-dropping alpine panoramas.

A grotto-like lodge decorated with gilded mosaics, rocks and a noisy waterfall was the setting for the most sumptuous pleasure house of 1900s Europe.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

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

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.