This 600-year-old home seems to defy physics.

A unique hanging cable-car navigates through Dresden, the oldest suspension railway in the world.

A German apartment building hosting as many trees as human occupants.

No need to strap in for a "ride" on this walkable roller coaster.

A church filled with the bones of hundreds of virgins martyrs—or so they say.

A stairway to heaven, or to nowhere at all.

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

This "floating railway" is one of the world's oldest monorail systems.

A tree-like building perches on its trunk in the Steglitz neighborhood of Berlin.

Skeletons dressed in extravagant 18th century royal costumes cavort in the aisles of this German basilica.

Ruins of a German Castle on top of a towering stone pillar.

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

One of the largest ochre quarries in the world, hidden in a limestone landscape.

The Church of the Annunciation was carved into the face of a cliff, just like the rest of the town of Haute-Isle.

A medieval church with largest and oldest collection of Renaissance frescoes in France.

A self-built mosaic house and sculpture park.

A mosaic-tiled house built by graveyard sweeper Raymond Isidore.

These quaint French houses dangle precariously over a precipice.

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

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

One of the greatest maze designer’s greatest mazes.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

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

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.