The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

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

The yawning maw of this pagan visage is said to bite off the hands of liars.

An alchemist's "magic door" stands in the middle of a Roman park.

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

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

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

Legend has it this fountain built to symbolize the Pope’s power hides a strange secret concerning Neptune's manliness.

Renaissance hospital featuring a rotating door into which unwanted babies were dropped.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

Before there were doorbells this bronze ear was installed for visitors to announce their arrival.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

The secret medieval communication system will whisk your words above the noise of the crowd.

This giant middle finger statue sends an unambiguous message to Italy's bankers.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

Catering to broken dolls for almost 200 years, this repair shop is now a charnel house of doll parts.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

The ruins stand as a somber reminder of France’s worst civil catastrophe of the 20th century.

Peeing dogs guard the Roman hunting goddess atop a fountain at France’s Château de Fontainebleau.