The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

The curious underground history of keeping Paris clean.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

An Art Nouveau building covered in animal gargoyles and grotesques.

A mysterious ancient cemetery with Roman sarcophagi and Lycian inscriptions.

Near the former site of numerous witch burnings, this lavish Edinburgh mainstay pays homage to Scotland's brutal history.

A patchwork of ruins from various civilizations in one of the world's oldest continually inhabited cities.

A monumental underground karstic wonderland is also the water source for over a million citizens of Beirut.

The largest hewn stone in history.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

Jesus' footprints and the first catacombs in the world.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

A perfectly circular lake is formed by the crater of an ancient underwater volcano.

This abandoned five-star hotel is now a five-star urban exploration destination.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

This Victorian marvel of engineering and artistic prowess is nicknamed the "Cathedral of Steam."

A spooky juxtaposition of caves and graves gives this legend-filled cemetery a particularly haunting vibe.

This unchanged Victorian park is rumored to have been the inspiration behind Peter Pan's Neverland.

When it came to designing his own small office building, the eccentric architect wasn't afraid to show the world what he could do.

When the public was consulted about a new piece of street art, they naturally asked for an enormous metal dragon.