This Roman arena once played host to bloody gladiatorial battles.

Long tunnels run under the ancient chariot racing circuit to the tower.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.

This luxury shopping lane has been protected by its own tiny police force for over a century.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

After nearly 60 years, there's still a bear at Paddington Station looking for help.

Eighty million natural history specimens call this gargantuan museum home.

This London pub hides a peculiar secret: a recreation of the rooms shared at 221b Baker Street by Sherlock Holmes and Dr. Watson.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

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

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

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

Pompeii's less famous neighbor is still revealing her secrets.

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

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

A hidden workshop for creating and restoring Papal mosaic masterpieces.

Breathtaking and huge 430 year old maps of Italy.

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

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

These lights mark the area of Rotterdam that was bombed and burned in 1940.

Europe's official "zero-level," the equator of elevation.

The history and future of cannabis.