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

An alchemist's "magic door" stands in the middle of a Roman park.

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

St. Francesca Romana, patron saint of drivers, resides in the church she founded.

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

A Nesting Doll of Churches.

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

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

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

Charles Dickens was not a fan of the ghastly wall dressings in this 6th century church.

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

This hill made entirely of ancient Roman jars was simply a garbage dump to the people of the time.

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

The final resting place of the poets Shelley and Keats.

Stone memorial that's said to predict the death of the pope and the site of the Cadaver Synod.

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

2300-year-old Roman road connecting the empire.

One of Catholicism's four major basilicas has a series of papal portraits that are said to predict the end of the world.

Jesus' footprints and the first catacombs in the world.

Largest necropolis in the Mediterranean.

The remains of a town so thoroughly destroyed by French forces that the citizens simply left.

The studio built by fascists in the hopes of "reviving the film industry" with the occasional propaganda film opportunity thrown in.

A secret hatch containing two parchments was discovered in this statue over 40 years after its installation.

A dead saint, a deadly poison, and a mysterious holy ooze.