Ancient mosaics, frescoes and marble floors emerge during routine works in Villa Celimontana.Archaeologists working in Rome's Villa Celimontana, a park near the Colosseum, have uncovered a substantial imperial-era building, complete with elaborate mosaics, painted ceilings and marble decoration, in a discovery that could reshape understanding of the Caelian Hill.  The find emerged during structural works funded by Italy's PNRR recovery plan, which were originally intended only to reinforce the historic retaining wall supporting the grounds of the 16th-century Villa Mattei.   Investigations by Rome's special superintendency, part of the culture ministry, revealed that what had been assumed to be a single wall was in fact two adjoining structures - and, behind the inner one, the remains of a building dating to the second century AD, later reorganised in the third century.   Excavators have fully uncovered five rooms and partially exposed three more, though the complex is believed to extend further towards Villa Mattei, where mature cypress trees and budget constraints have prevented complete excavation. Mosaics The building's largest room features a geometric mosaic floor centred on a marine-themed emblem: a dolphin, a fish, a lobster and a crab arranged around a large two-handled vase known as a krater.   A fragment of an earlier mosaic floor, thought to date from the Antonine period, was also found beneath it, alongside extensive collapsed sections of a frescoed ceiling decorated with red and blue circles framed in white stucco. Traces of opus sectile - inlaid marble panelling - point to a lavishly decorated interior throughout.   The building appears to have been abandoned between the fifth and sixth centuries, later partly disturbed by the construction of Villa Mattei's loggia, and eventually buried under layers of soil dating mostly from the late 18th and early 19enturies. Domus or fire brigade barracks? The quality of the decoration suggests a high-status residence, or domus, of the kind found elsewhere on the Caelian Hill's summit.   However, the building's proximity to the known base of the Fifth Cohort of the Vigiles - Rome's night-watch and firefighting corps - has led researchers to consider an alternative theory: that the structure formed part of the cohort's barracks.   Villa Celimontana excavation site. Photo: Fabio Caricchia   Supporting evidence includes earlier discoveries of small modular rooms likely used as lodgings for the Vigiles, as well as two statue bases inscribed with lists of cohort members, found nearby in 1820. The krater motif in the mosaic also echoes decoration found in two leisure rooms of the Vigiles' barracks at Ostia. Some researchers now suggest the barracks complex may have been considerably larger than previously thought, potentially covering much of the plateau and including fortified perimeter structures, officers' quarters and a shrine, or Augusteum, echoes of which may survive in coloured marbles later reused in the Vatican's Sala Regia. Ministry hails PNRR-funded find Culture ministry chief of staff Valentina Gemignani described the discovery as a demonstration of how conservation work can evolve into archaeological research.   Superintendent Daniela Porro said the funds, originally allocated to secure an ancient wall, had also enabled a discovery of considerable scientific value.   Simona Morretta, the excavation's scientific director, said the site had already yielded data of exceptional interest, but that the more delicate work - analysing the structures, materials and archaeological context to test the competing interpretations - was only just beginning.   Photo credit: Fabio Caricchia

Villa Celimontana excavation site. Photo: Fabio Caricchia   Supporting evidence includes earlier discoveries of small modular rooms likely used as lodgings for the Vigiles, as well as two statue bases inscribed with lists of cohort members, found nearby in 1820. The krater motif in the mosaic also echoes decoration found in two leisure rooms of the Vigiles' barracks at Ostia.