A sewer might be no place for an emperor, but it is precisely from an ancient drainage system that archaeologists have dug-up a large marble sculpture of Constantine, one of Rome's greatest leaders.

Archaeologists found the 24-inch-tall head last week while clearing up a sewer in the Roman Forum, the center of public life in the ancient city, said Eugenio La Rocca, superintendent for Rome's monuments.


"We can't be sure of why it was put there," La Rocca said Thursday at a news conference during which authorities showed the bust to the media.

One possibility is that the sculpture of the man who reunited the Roman Empire in the early fourth century and ended years of persecutions against Christians was unceremoniously used later to clear a blocked sewer, he said.

La Rocca called the statue a rare find, saying that its insertion in the sewer probably saved it from the plundering the Forum suffered after the fall of the Roman Empire in the fifth century.

"Many portraits have been found in Rome, but these days it's not easy to find one, especially of this size and so well preserved," he said.

Experts confirmed that the sculpture portrays Constantine by comparing it to coins and two other giant heads of the emperor that are kept in Rome's Capitoline Museums, La Rocca said. The Carrara marble head probably belonged to a statue of the emperor in full armor, and was erected in the part of the Forum built by the emperor Trajan after Constantine conquered Rome from a rival in A.D. 312.

The style and stern features used in all of Constantine's portraits also recall the traits of Trajan, who expanded the empire to its maximum size in the early second century.

"Trajan was the greatest emperor and Constantine considered him a model," La Rocca said

During his reign, which lasted from 306 to 337, Constantine tried to stop the fracturing of the empire and sought to restore it to its ancient glory. Although not a Christian himself, he ended the frequent waves of anti-Christian persecutions by proclaiming religious freedom throughout his lands. He also moved the empire's capital to Constantinople -- today's Istanbul -- closer to the Eastern borders threatened by the barbarian invasions.

La Rocca said that restorers will now take charge of the work, which will probably be put on display next year in a museum being built in the Roman Forum.