A World War I German experimental concrete plant, hidden deep in a French forest.

These bronze horses on the gates of the Royal Palace of Naples were a gift from a Russian tsar.

This amazingly well-preserved villa just outside Pompeii boasts rare examples of ancient Roman paintings.

Before it was buried by volcanic ash, this fast-food restaurant fed the hungry hordes of ancient Rome.

Ancient snack bar of the Roman Empire re-opened.

The walls and streets of the ancient city are peppered with penises.

Erotic art covers the walls of the largest ancient pleasure palace.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

San Gennaro, the patron saint of Naples, greets pedestrians between these narrow city streets.

This medieval city gate is now a blend of the past and the modern world.

This monumental fountain has moved around the city multiple times.

According to the legend, this structure was built in a single night with the help of the devil.

A secret hatch containing two parchments was discovered in this statue over 40 years after its installation.

The mysterious “claw marks” said to be left by the Devil on Pisa’s famous cathedral.

Hilltop garden on the site of an old fortress overlooking the Mediterranean Sea.

A bronze tribute to Mika Häkkinen's 1998 Monaco victory.

This peaceful open space below Geneva's famous cathedral is full of art and history.

A swath of France so devastated by war it is still forbidden to go there.

Site of one of World War I's most horrific scenes.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

A towering baroque basilica jutting out of the French countryside.

This striking fort on the Maginot Line looks just as it did after being destroyed in the Fall of France.

Wooden pavers represent a 17th-century barrier that gave Wall Street its name.

Walk down these stairs to get an underwater view of Switzerland's Lake Zug.