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

A wunderkammer of mysterious objects and stories.

This 16th-century monastery has been turned into a surrealist architecture compound.

Soaring over 6,000 feet in the Bavarian Alps, this beer garden was once Hitler's 50th birthday present.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

These 18th century gardens tell a rocky story of the son of Odysseus.

This salt marsh in Southern France is as pink as the flamingos that inhabit it.

A Gothic cathedral created from volcanic rocks.

This museum tells the story of lake dwellers from 4000 BC to 850 BC, replete with stilt houses and goats.

The sinister ruins of one of the worst dam failures of the 20th century lie in this astonishing alpine setting.

Money made from smuggling sugar helped create this wondrous rock maze in honor of the Prussian Queen Louise.

Romania's "Red Ravine" is a little-known natural wonder that bears a resemblance to the Grand Canyon.

Since ancient times these picturesque springs have been providing bathers with healing waters.

When a medieval fire claimed the original St. Stephen’s Cathedral, it sparked a pattern of unquenchable organ building.

The architect of this fanciful complex called it an "oasis for humanity and nature in a sea of rational houses."

The deserted pirate-themed restaurant still entices explorers.

Resting in the middle of an Austrian river, this sci-fi "island" lets people cross in neon style.

An open-air museum in a mountain valley features works designed to blend in with—and disintegrate back into—their natural surroundings.

The "stairway to heaven" lookout tower was built to resist weather, arson, and the laws of physics.

As lake waters recede, a German village reemerges after more than a hundred years.

The highest point in Belgium is a staircase to nowhere.

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

Abandoned railway line circling the city of Paris.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.