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

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

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

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

This one-of-a-kind Roman arch is not actually dedicated to the god Janus.

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

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

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

The yawning maw of this pagan visage is said to bite off the hands of liars.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

Architectureal fantasy quarter of Rome.

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

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

An ancient and majestic fortress that played an integral role in Portugal's road to independence.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."