A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.

Plenty of old carney magic still haunts this photogenic amusement park.

Ancient man-made caves underneath small town Belgium.

This ghost town in Belgium will lose its street art when it ceases to exist.

Whimsical sculptures and caves chiseled by nature over the millennia.

A breathtaking canyon offers stunning views and frightful pathways through an ecological paradise.

A self-built mosaic house and sculpture park.

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

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

Abandoned blockhouses from Nazi Germany's Atlantic Wall erode into the sea on a French beach.

A charming Spanish village sits atop this natural limestone overpass.

This narrow path was cut right into a French mountainside to feed the country's early naval expansion.

This funky former tobacco factory is one of the most striking examples of Madrid's cultural diversity.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

A open air theatre built on a cliff by an eccentric British woman.

Six beautiful wooden giants are hidden around Copenhagen.

Vortex-shaped aquarium hosts Europe's largest school of piranhas and other ocean creatures.

Colorful lights and mirror-like brine pools create trippy illusions within the historic mine.

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

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

Abandoned for decades, trains still pass through the now-restored remains of one of Madrid's first metro stations.

This enchanting hamlet carved into the rock looks like something straight out of Tolkien's Rivendell.

The abandoned remains of this Victorian brewery hide crumbling bowling alleys and rusting industrial gear.