This former steel and coal plant is now a neon-lit industrial fantasia.

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

This historic stone bridge has an entire neighborhood clinging to its sides.

The home of the morbid art of corpse plastination is open for visitors to view the fascinating, but stomach-churning process.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

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

This French "sea of rocks" is packed with stunning rock formations and its own medieval castle.

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

This former quarry is now a picturesque gorge that hides a sunken lake.

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

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

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

A striking 12th-century-style castle built on the edge of a cliff.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

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

Underneath a chalk hill in France lies what Hitler hoped would be the underground launching base for a devastating new weapon.

A centuries-old complex of hand-dug stone chambers has sheltered locals in times of trouble.

This beautifully designed star-shaped fort was the premier defense system of the late 1500s.

Hiding the longest subterranean river known in the world.

This tri-part waterfall is a little bit of fairytale beauty in the heart of Luxembourg's Little Switzerland.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

An underground city of ancient quarry tunnels hid thousands of Allied soldiers in WWI.

A sprawling Baroque park with 300-year-old hydro-pneumatic waterworks.

Between Neo-Pagans and Neo-Nazis, these strange rock formations have a curious cult following and a very strange history.