Rome unveils restored wall mosaic that may be the Roman world’s largest

A monumental wall mosaic hidden beneath Rome has been restored and unveiled ahead of small-group public visits. Archaeologists describe it as the largest example known in the city and possibly anywhere in the Roman world. The first-century artwork survives in an underground gallery below the Baths of Trajan on the Oppian Hill, near the Colosseum.

Arranged across several levels, the mosaic creates the illusion of grand architecture populated by human and mythological figures. Recent excavation exposed an additional lower band showing a fortified harbor city, with walls, towers and buildings facing the water. Researchers do not yet know whether it represents a real place, such as ancient Ostia, or an idealized city. The room’s richly decorated walls may once have risen to about 12 metres.

The conservation project also restored the Painted City, a roughly 10-square-metre fresco offering a bird’s-eye view of a walled Roman settlement. New walkways, lighting and controlled access will allow visitors to see both works while limiting pressure on the fragile surfaces. Displays also include lead water pipes from the baths.

The gallery preserves structures that predate the vast bathing complex, inaugurated in AD 109. Scholars are still debating whether they belonged to Nero’s Domus Aurea or a later building. Excavations will continue, leaving open the possibility that more of the site’s layered history remains underground.