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

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

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

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

The remains of this 2nd-century Roman temple are incorporated into a modern building.

A rare example of a medieval house in Rome adorned with a melancholic inscription.

A 16th-century horror show built in a lovely Italian garden.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

One of Amsterdam's narrowest houses is located right across the canal from its widest.

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

The former headquarters of history's oldest megacorporation.

This is the oldest Roman-made bridge in the city still existing in its original state.

Breathtaking and huge 430 year old maps of Italy.

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

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

The commemorative stone column conceals a secret laboratory.

The Great Fire of London and the regulation of one-way streets both started in this alley.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

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

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

Experience what life was like in Ireland during the Viking and medieval ages.

Monasteries on rock pillars, once accessible only by frayed ropes.

Ancient Greek oracle of the dead.