A part of the mosaic floor being excavated. EDOARDO RUSPANTINI

Researchers studying an underwater city in Italy say they have found an ancient mosaic floor that was once the base of a Roman villa, a discovery that the local mayor called "stupendous."

The discovery was made in Bay Sommersa, a marine-protected area and UNESCO World Heritage Site off the northern coast of the Gulf of Naples. The area was once the Roman city of Baia, but it has become submerged over the centuries thanks to volcanic activity in the area. The underwater structures remain somewhat intact, allowing researchers to make discoveries like the mosaic floor.

The Campi Flegrei Archaeological Park announced the latest discovery, which includes "thousands of marble slabs" in "hundreds of different shapes," on social media.

"This marble floor has been at the center of the largest underwater restoration work," the park said, calling the research "a new challenge" and made "very complicated due to the extreme fragment of the remains and their large expansion."

The marble floor is made of recovered, second-hand marble that had previously been used to decorate other floors or walls, the park said. Each piece of marble was sharpened into a square and inscribed with circles. The floor is likely from the third century A.D., the park said in another post, citing the style of the room and the repurposing of the materials as practices that were common during that time.

Researchers are working carefully to extract the marble pieces from the site, the park said. The recovery work will require careful digging around collapsed walls and other fragmented slabs, but researchers hope to "be able to save some of the geometries."

Once recovered, the slabs are being brought to land and cleaned in freshwater tanks. The marble pieces are then being studied "slab by slab" to try to recreate the former mosaic, the park said.

"The work is still long and complex, but we are sure that it will offer many prompts and great satisfactions," the park said.


The remains of collapsed walls that cover the mosaic floor. PARCO ARCHEOLOGICO CAMPI FLEGREI