The remains of a convent turned military barrack in the heart of Madrid.

This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

A rather vulgar example of the transition from Latin to the Italian vernacular.

These hut foundations are believed to be the residence of Romulus, founder of Rome.

An ancient Egyptian temple in the middle of Madrid, Spain.

The facade of this 16th-century building is decorated with carvings of 300 seashells.

The Cathedral of Salamanca has a number of unusual carvings but none so surprising as a modern astronaut.

An unremarkable wooden wheel built into the side of one of Rome's oldest hospitals was part of a policy to reduce infant exposure.

Legend has it that this bronze orb, which sat atop an ancient Egyptian obelisk, once held the ashes of Julius Caesar.

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

Its interior is adorned with some of the best examples of early Christian mosaics.

Gods clash with machines in a power plant regenerated as a museum.

The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

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

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

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

A Nesting Doll of Churches.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

Jesus' footprints and the first catacombs in the world.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

A fairy tale castle in modern Rome.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

2300-year-old Roman road connecting the empire.

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