The Roman Emperor's lost summer home and grotto full of enormous sculptures sit along the Italian seashore.

A tree that defies gravity grows in an ancient ruin.

A massive marble foot is tucked away in a small alley near the Pantheon.

The fragmented remains of a massive public bath connected to the city's water supply.

Virgil's many-mouthed gateway to the underworld.

A submerged archeological park still holds the wonders of a Roman Sodom.

The Bourbon royal family had this unique octagonal hunting "cottage" built on a tiny islet in Lake Fusaro.

A mushroom-shaped outcropping that has come to be the symbol for an entire town.

Deceased nuns were placed on stone chairs to decompose, while the surviving nuns prayed near the lifeless bodies.

The oldest stone house in Paris was built by its most famous alchemist.

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.

France's most famous cemetery, with some of its most curious tombs.

The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.

One of the only Florida forts to remain in the hands of the Union all through the Civil War still stands as a historic stronghold.

The remnants of the fortress that saved Georgia from the Spanish still stand guard on their swampy island.

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

The medieval town's star-shaped walls are geometrically dazzling, though not entirely impenetrable.

A Belgian self-built tower inspired by the Bible and ancient civilizations.

This historical Netherlands fortress still bears the marks of its single siege.

A luxury hotel housed in a former 15th century Gothic church.

Incredible labyrinth of man made caves.

This sprawling Belgian fort was once thought of as impenetrable but now it is simply an abandoned relic.

A natural tidal swimming pool is ringed by bizarrely artistic lava rock formations.