The city sank primarily because of the bradyseism phenomenon, where the volcanic ground slowly rises and falls.
Much of the site was once the playground of Roman emperors like Nero and Caesar, who owned villas in the area.
Original statues from the Nymphaeum are displayed in the Archaeological Museum of the Campi Flegrei, with replicas placed underwater in their original positions.
The park is one of the few places worldwide where you can snorkel or dive directly over active archaeological excavations.
Traces of black-and-white mosaics (opus tessellatum) are still visible on the sea floor.
The submerged streets follow the precise layout of a standard Roman urban plan, including intersections and drainage systems.
The entire coastal area is part of a larger volcanic system known as the Phlegraean Fields, which remains geologically active.
Evidence of lead pipes, known as fistulae, can still be identified in some submerged wall structures.
The Underwater Archaeological Park of Baia is a protected marine area featuring the submerged ruins of a Roman resort city that sank due to bradyseism. The site sits on the floor of the Phlegraean Fields, a volcanic caldera, where thermal activity caused the ground to subside over centuries. Visitors can view the remains of paved Roman roads, mosaic-tiled floors of elite villas, and sculptural porticos through glass-bottom boats or scuba diving. The most famous submerged features include the Nymphaeum of Punta Epitaffio and the remains of private thermal baths. The archaeological zone covers approximately 177 hectares at depths ranging from 2 to 15 meters. It is legally designated as a Protected Marine Area to preserve the structural integrity of the ancient maritime structures.
The Nymphaeum of Punta Epitaffio, often accessible via guided dive tours.
Book a glass-bottom boat tour if you are not a certified scuba diver to see the ruins without getting wet.
Bring an underwater camera or GoPro as the visibility can be excellent on calm days.
Ensure you book through authorized diving centers that hold the specific permit to operate within the marine protected area.
Attempting to visit or dive the site independently without a licensed guide, which is prohibited by law.
Open year-round, though diving activity is heavily dependent on sea conditions and may be cancelled during adverse weather.
Strictly no-touch policy; visitors must not disturb the stones, mosaics, or marine life to prevent structural damage.
