Parco Sommerso di Baia

The submerged archaeological park of Baia preserves Roman villas, a nymphaeum and the remains of Portus Julius beneath the waters of the Phlegraean coast. The ruins record the gradual submergence of a Roman resort landscape through bradyseismic movement.

Why it matters

The underwater remains document the scale and character of Baiae, a Roman coastal settlement whose lower terraces were overtaken by the sea. The protected area, established in 2002, includes archaeological sites along the coasts of Bacoli and Pozzuoli and combines marine conservation with the study of submerged heritage.

What to notice

The residential remains include Villa dei Pisoni and a villa with an entrance porch rising from the water. The nymphaeum associated with Emperor Claudius was excavated from the seabed in 1981–82; its sculptural programme is displayed in the museum at the castle above. Portus Julius, built in 37 BCE under Agrippa, preserves the submerged basins, warehouses and channels of a major naval harbour. Mosaics and wall lines show the shape of the ancient buildings beneath the water.

Context and history

Bradyseismic cycles gradually submerged parts of Baiae, Pozzuoli and Misenum from late antiquity onward. Chance finds in the 1920s renewed interest in the underwater remains, followed by archaeological research from the 1960s and the excavation of the Claudian nymphaeum in 1981–82. A 2002 decree established the marine protected area and divided it into zones with different levels of protection. The site is both an archaeological landscape and a record of the Phlegraean Fields' changing coastline.