The first green space constructed on an elevated viaduct.

This museum houses an imposing skeleton army comprised of creatures great and small.

Paris' linguistic guide to the international language of, yes, love.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

This amazingly preserved Doric temple was abandoned before it was ever completed.

One of the largest squares in Europe contains an entire artificial island.

This deceiving white sand beach gets its brilliant hue from the chemical discharge of a nearby factory.

A long-buried ancient ruin unearthed right in the middle of the city.

Massive galleon from a box-office bomb docked in Genoa.

Psychoanalyst Carl Jung reported a paranormal experience after visiting this mosaic-lined Roman baptistry.

A medieval, mosaic-lined baptistry built by a heretical Christian sect.

An incredible mosaic-lined monument said to have held the remains of an ancient Roman empress.

A mysterious ancient elephant said to possess magic powers is now the symbol of a Sicilian city.

This peculiar Italian elevator runs both horizontally and vertically.

This cathedral hides a sculpted dog that determines your fate and an unexploded shell from World War II.

This 6th-century church has the largest and best-preserved collection of Byzantine mosaics outside Constantinople.

Italy's curious field of mud volcanoes is named for being both gross AND salty.

This bustling Italian plaza is built on the ruins of an ancient Roman amphitheater.

This Arabesque Italian castle was built with a primitive, if ingenious, air-conditioning system.

Explore the quarry where the marble was sourced for Michaelangelo's David.

Italian poet Dante Alighieri is entombed in this small mausoleum in Ravenna, and his hometown of Florence has never been too happy about it.

"Stairs of the Turks", a chalky white cliff eroded conveniently into stairs, allowing for easy pillaging.