Underwater surveys of the submerged archaeological park of Baia off the coast of Naples have revealed new elements of the ancient Roman luxury villas lost beneath the waves. An exploration of the Baths of Lacus, a private thermal bath built inside a domus, found a section more than 260 feet long with visible remains including a stone colonnade with collapsed columns made of fine imported Portasanta marble from Chios in Greece. A large section of opus sectile (marble inlay) flooring was also discovered. It too was made of Portasanta marble, but in alternating colors. This style of decoration was typical of Late Antiquity.
The coastline of Baia was subject to bradyseism — cycles of subsidence and uplift — for thousands of years thanks to its location in the Campi Flegrei caldera. The Roman-era coastline was in a subsidence cycle that left the villas of the elite, including the palaces of emperors between the 1st and 3rd centuries, in constant danger of being submerged. Uplift began in the 10th century, and today’s sea level is more than 30 feet above Roman-era sea level.
The Submarine Park of Baia was established in 2002 as a protected marine area that preserves both the environmental and archaeological patrimony of the site. Interference with the archaeological remains is prohibited, as are underwater fishing, pollution, even swimming in certain areas. The Lacus Baths site is a new part of the park established in 2020 to allow scuba tourists and snorkelers to explore the bath’s exceptional mosaic floors made with white, pink, red, green, grey and black tiles.
The Lacus Baths also provide a unique glimpse into the Roman efforts to combat subsidence. Large columns were placed horizontally along the end of the domus to act as barriers against water penetration, and the floors raised repeatedly. It didn’t work in the long term, clearly, as the remains of the baths are now 13 feet under the surface of the water.