

In the year 300 AD, Christianity was a minority religion in the Roman Empire, practiced by perhaps ten percent of the population. In good years it was discriminated against; in bad years it was persecuted. By 400 AD, a century later, it had become the official religion practiced by pretty much everyone. Evidence of this remarkable transformation can still be seen in Rome’s monuments.

Teachers in Sunday schools like to tell a story about how it happened.

In the year 312 there ruled a Roman Emperor named Maxentius who had taken power illegally. He hated Christians and persecuted them. The proper heir to the throne, Constantine, marched on Rome to save the Empire. Before the two forces met in battle, Constantine saw a vision of a cross in the sky and the words “Conquer under this”. Constantine and his army converted to Christianity and painted the cross on their shields. The next day they defeated the pagans and brought Christianity to Rome.

This story is almost entirely wrong, yet it has resonated down the centuries through books, paintings, and films to become part of the Christian legend.

The truth is more complex. Maxentius and Constantine were both sons of emperors and thus equally legitimate. Maxentius did not persecute Christians, and the story of Constantine seeing a cross in the sky doesn’t appear in the texts until years after the battle. Constantine did defeat Maxentius and marched into Rome in triumph, bearing his rival’s severed head as a trophy. After the usual celebrations and gladiator spectacles, he built the Arch of Constantine, which has no Christian symbolism but does depict sacrifices to four pagan gods. In later years he built a number of grandiose churches, including the original St. Peter’s, but didn’t get baptized until his deathbed. Paganism remained legal throughout his reign.

Constantine gave one great boon to the Christians–he legalized their religion. From then on it rapidly gained more followers and began edging out the pagan cults. Soon it was the pagans being persecuted. Rioting monks trashed temples and killed pagan philosophers like Hypatia. In 382 the Altar of Victory was removed from its centuries-old home in the Senate. In 391 paganism was outlawed and temples shut all over the Empire. The old cults hung on for a few generations in rural areas, but Christianity was now the dominant power.

Traces of this incredible transformation are visible in Rome. At the Basilica di San Clemente a 12th century church is built atop a much earlier church. This earlier building was the home of a Roman noble, a secret Christian who invited fellow Christians into his home to worship, a common practice in the days when Christianity was illegal. Underneath his home lies a subterranean temple to the pagan god Mithras.

Entering the medieval church you see the usual grandiose paintings and sculptures. The real interest comes when you descend the stairs into the dank, dark cellar. There you can see the original church much as it was. Descend further and you get back to the days of the pagan Roman Empire. Three rooms survive. One may have been a mint. Another, with a few paintings surviving, was a training room for acolytes in the Mithraic faith. The third is the temple, or mithraeum, for Mithras himself.

%Gallery-102749%Mithras was Christianity’s main rival. As a mystery religion with its deepest teachings revealed only to the initiated, we don’t know much about its inner workings. What we do know shows many similarities between Mithraism and Christianity, such as the belief that Mithras was born on December 25 to a virgin, and died and was resurrected in order to save mankind. The similarities were so numerous that early Christian writers said that the older religion was invented by the Devil as a cheap imitation of Christianity before Jesus was even born!

The mithraeum is a long, rectangular room with benches to either side. Members would sit on these benches and share a communal meal that included bread and wine. At the end of the room stood a plaque showing Mithras in a little-understood ritual of killing a bull. Mithraism was popular, but didn’t have the widespread appeal of Christianity. First off, only men were allowed into the cult. Also, most of the teachings were secret, and while that had a certain mystique, it also turned off many who didn’t want to go through a long period of study and initiation. Despite this more than a dozen mithraea survive in Rome and there were probably hundreds during its heyday.

The transition from pagan to Christian isn’t always as obvious as in San Clemente. Sometimes you can see it in the art, such as the image above, a 4th century mosaic from Santa Pudenziana. Here Christ sits enthroned in a pose identical to many statues of the pagan god Jupiter. Saints Peter and Paul sit to either side dressed as Roman senators. The early Christians saw nothing wrong with this. They wanted to win the hearts and minds of the people, and a bit of reworked pagan symbolism was a good way to do that.

At times the Christians reused old buildings or parts of old buildings. San Maria Maggiore, a third century basilica, was originally a secular building before being converted into a house of worship. This is one of the most stunning churches in Rome, with fifth-century mosaics showing Biblical scenes and a ceiling gilded during the Renaissance with the first gold brought back from the New World. So many Roman sites are only foundations with perhaps a few columns standing, but here you can actually stand inside a Roman building.

Christianity would have never caught on so quickly if it didn’t have the Empire’s infrastructure to spread its message. These were the days when trying to cross a border could easily get you killed, and the Empire provided a large, secure area in which to move about. The Catholic Church understood their debt to Rome and wanted to take on its aura of glory and power. Rome went became the capital of the new faith and its art and architecture was incorporated into churches worldwide. The Church was still trying take on a bit of the old Roman magic as late as the 17th century, when the Pope ordered the giant bronze doors from the old Roman Senate installed in the entrance to St. John Lateran.

The name Roman Catholic Church is no accident.

Don’t miss the rest of my Vacation with the Dead: exploring Rome’s sinister side.

Coming up next: Saints’ relics in Rome!