It's more that the land has subsided, rather than the sea level rising. The article mentions that this is due to volcanic activity, and I had a bit of a dig and

It's more that the land has subsided, rather than the sea level rising. The article mentions that this is due to volcanic activity, and I had a bit of a dig and found: https://rischi.protezionecivile.gov.it/en/volcanic/volcanoes-italy/phlegraen-fields/ https://rischi.protezionecivile.gov.it/en/volcanic/volcanoes... -- the area, including a lot of the Gulf of Pozzuoli, is part of a volcanic caldera which is still sufficiently active that the ground level gradually sinks and occasionally rises as the magma chamber underneath empties or fills. The area is the main cited example in the wikipedia article for the phenomenon: https://en.wikipedia.org/wiki/Bradyseism https://en.wikipedia.org/wiki/Bradyseism .