The vast, legendary catacombs hold secrets much stranger than stacked bones.

An ancient Egyptian obelisk is now used to commemorate fallen Italian soldiers.

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

The only remaining arch of the oldest stone bridge in Rome stands in the middle of the Tiber.

Romans decided this 16th-century "talking statue" was so ugly, they named it after a primate.

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

This hydrochronometer was invented by a Dominican monk and is a prime feature in this garden.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

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

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

A forgotten "city of water" underneath the famous Trevi district.

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

This large, circular tomb is the final resting place of the first emperor of Rome.

The "Great Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

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

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

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

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

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