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

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

Time has been frozen at this station since the bombing in 1980—or so it was believed.

This small church was constructed over the ruins of three temples dating to the Roman Republic.

Plaques on its facade commemorate the Tiber's most destructive deluges.

A striking memorial recalls thousands of Bolognese men and women killed fighting fascists in World War II.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

This curious, round temple is the oldest still-standing marble building in Rome.

This small, ancient Roman temple was once a church dedicated to the patron saint of penitents.

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.

The roof of this ancient mausoleum is made from a single Istrian stone weighing a massive 230 tons.

This ancient market is often referred to as the oldest shopping mall in the world.

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

This one-of-a-kind archeological site is home to strange prehistoric ruins, the original use of which is still a mystery.

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

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

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

This Roman statue is missing a limb from when the Venetians stole it from Constantinople during the Crusades.

Also known as the Square Colosseum, this building is a prime example of fascist-era rationalist architecture.

A copy of the famous statue can be found in this Florence piazza, along with one of the most breathtaking views of the city below.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.