Archaeological ruins have been found as construction workers were upgrading Rome's public transport.

According to reports, the barracks cover 900 square meters include 39 rooms adorned with black-and-white mosaics on floors and frescoed walls.

A collective grave with 13 adult skeletons with bronze artefacts was also found.

According to the culture ministry officials, the barracks are believed to have been used by Praetorian guards, dating back to the second century A.D.

The discoveries were unearthed by archeologists who were at the new underground line at Amba Aradam, the city's third metro line. It is scheduled to operate in 2020.

Rossella Rea of Culture ministry told Associated Press that the discovery characterizes the area as a military neighborhood.

"It's exceptional, not only for its good state of conservation but because it is part of a neighborhood which already included four barracks," she said.

"And therefore, we can characterize this area as a military neighborhood," she continued.

The Praetorian Guard was created by Rome's first emperor, Augustus. They are thought to be one of the ancient world's most prestigious military units as they served as the emperors' bodyguards. Aside from being a fighting force, they also served as emergency firefighters, since fire is common during their time. Fire was also being performed at the roman games and played in bloodshed to show their combat expertise and thought to have murdered several emperors despite pledging their service for them.

History.com revealed that the structure of the Praetorian Guard ended when Constantine reassigned its members to the outskirts of the Empire, and ordered the destruction of their barracks at the Castra Praetoria.

Roman Empire covers nearly two million square miles, and currently, remnants of which are still being uncovered throughout Europe.

According to BBC, the discovery would not delay the Metro station's opening, but may result in some adjustments to its design.