Construction to a Roman subway line has unearthed an ancient military neighbourhood buried beneath the city.

As builders continue construction nearby, archaeologists on site are working to recover the artefacts contained within the barrack's expanse of 39 rooms.

The dig also revealed a collective grave, containing numerous skeletons and a bronze bracelet.

Construction to a Roman subway line has unearthed an ancient military neighbourhood buried beneath the city. Pictured above, an archeologist checks human bones as ancient Roman ruins of former barracks were discovered during work on a new underground line (AP Photo/Alessandra Tarantino)

Culture ministry officials on Monday showed reporters where work on the city's third subway line unearthed barracks for Roman Praetorian guards dating back to the period of Emperor Hadrian, in the second century A.D.

While construction workers poured concrete at the planned Amba Aradam metro stop, an archaeologist just a few meters away brushed dirt from a small bronze bracelet.

The barracks, discovered nine meters (about 30 feet) below street level, cover 900 square meters (9600 square feet) and include a long hallway and 39 rooms decorated with black-and-white mosaics on the floors and frescoed walls.

'It's exceptional, not only for its good state of conservation but because it is part of a neighbourhood which already included four barracks,' said Rossella Rea of the Culture Ministry.

'And therefore, we can characterize this area as a military neighbourhood.'

Archaeologists have also found a collective grave at the barracks, where they have so far discovered 13 adult skeletons along with a bronze coin and a bronze bracelet.