Ancient clue cracks open a 2,000-year-old mystery near famed Colosseum

The building, which dates to the second century A.D., was found in the Villa Celimontana park near the Colosseum, Reuters reported this month.

At the excavation site, archaeologists fully uncovered five of the building's eight rooms, which contain mosaics and remnants of painted decorations.

Officials believe the building may have been part of the nearby barracks of the Fifth Cohort of the Vigiles, ancient Rome's firefighting force.

They cited one telling clue: A mosaic found at the site closely resembles one previously discovered in a firefighters' barracks in Ostia, ancient Rome's port city.

"If this hypothesis is confirmed, the discovery would help reassess the extent of one of the most important military complexes of imperial Rome," officials said in a statement.

Pictures show the remains of the ancient building, including exposed walls and sections uncovered during the excavation.

Other images show fragments of mosaic uncovered at the site.

Another possibility, said officials, is that the structure was a private residence, or domus, similar to others found on Caelian Hill.

The elaborate decorations could support that hypothesis, officials said.

"Only a thorough study of the excavation materials and the structures exposed will provide further information on the newly discovered structure," the superintendency said.

Reuters contributed reporting.