An incredible mosaic-lined monument said to have held the remains of an ancient Roman empress.

The roof of this ancient mausoleum is made from a single Istrian stone weighing a massive 230 tons.

Numerous stone coffins from different centuries, lined up in a sixth century basilica.

A rare example of an octagonal Catholic church.

Two stone columns flank the grand Venice square, but there were supposed to be three.

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

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

Believed to be the remains of the lost Temple of Minerva, this nymphaeum has been known by its misnomer to this day.

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

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

A monumental fountain in Rome features a large statue of Moses that has been criticized for centuries.

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

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

A massive marble foot is tucked away in a small alley near the Pantheon.

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

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

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

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

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

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

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

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

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

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