Countless stories attempt to explain Poland's mysterious J-shaped trees.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

This semi-secret storybook hedge maze is also the oldest garden in the city.

Legends of time travel and magical woodland creatures bolster the natural charm of this verdant sanctuary in the midst of Moscow.

Submerged busts of communist and socialist figures from the USSR.

The largest catacomb system in the world.

A subterranean Holocaust refuge within one of the world's longest cave systems.

Bordered by forest on three sides and the ocean on the other, the Great Dune of Pilat is the highest sand dune in Europe.

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

This natural French spring has been turned into a magical grotto by Roman and medieval constructions.

"In the Dark" Restaurant in Paris offers dinner in complete darkness.

This Parisian café sticks almost exclusively to an ethos of reuse.

Explore the complex ecology of this multifaceted nature preserve by riverboat.

This series of underground chambers contains Europe's largest subterranean lake that is slowly drained each day.

The topiary maze at the Habsburg hunting lodge.

This outsider art house has gone from clinical creation to astounding artwork.

The deepest sinkhole in Central Europe comes with a grisly tale and an unusual nickname: “The Stepmother Abyss.”

This network of conjoined cellars was riddled with traps and supposedly allowed the townspeople to pretend their homes were deserted.

A musical instrument played by the sea.

This one-time health resort was used by aristocrats around the world.

This massive subterranean fissure is known as the "underground Grand Canyon."

A miniature train-ride through Slovenia's largest cave system.

The remains of a sunken military ship wreck visible through clear water.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.