The submerged Baia Park includes all of the ancient shoreline that extends from the current port of Baia to the “Pontile dei Pirelli” a Pozzuoli. This area includes part of the Baia territory and the Porto Iulius complex, composed of the basin and of numerous environments dedicated to the storage of goods. The actual conformation of the landscape greatly differs from the ancient layout of the territory due to the submersion, following the bradyseism, of the entire coastal strip.
The Marine Protected Area called "Submerged Park of Baia" was established with the Interministerial Decree of 7 August 2002 by the then Ministry of the Environment (today the Ministry of ecological transition in agreement with the Ministry of Cultural Heritage and Activities (today the Ministry of Cultura - MIC), Infrastructure and Agricultural Policies, in agreement with the Campania Region).


Baia was a residential center renowned for its mild climate, the beauty of the landscape and the wealth of beneficial thermal waters, exploited since the 1st century BC. It was a privileged holiday resort for the Roman aristocracy and the imperial family until the end of the 3rd century AD. 
The bay of Baia was occupied by a lake (Baianus locus), communicating with the open sea through a large canal, on whose banks there were numerous villas equipped with landings and fish ponds. Among the most illustrious owners of villas there were the Scipioni, Gaius Mario,Julius Caesar, Cicero, Pompeo Magno, Marco Antonio and the emperors themselves, who built an imperial palace in Baia where Augustus, Tiberius, Claudius, Caligula, Nero, Adriano and Alessandro Severo stayed.
An example of the building density and urban fabric of the ancient Bay is still preserved on the ground inside the Archaeological Park, where villas and public and private spa complexes intersect. Of this monumental building, much celebrated by literary sources, the three large round rooms with domed roof still stand out, defined by the literary tradition as "temple of Mercury" (the oldest example of a hemispherical dome), "temple of Diana" and " temple of Venere ": in spite of their denominations, these are imposing thermal rooms. 
The first signs of the slow downward movement that led to the disappearance of the coastal strip began at the end of the 4th century AD. The inexorable sinking of the coast caused the abandonment of the maritime villas, but also allowed the remains to reach the present day, preserving some evidence of the ancient splendor.
In 1969 at Punta Epitaffio there was the causal discovery of two marble statues, disfigured at the head by marine lithodomes, in which two protagonists of the famous scene of the drunkenness of Polyphemus were recognized: Ulysses who hands Cyclops the cup full of wine, while one of his companions pours some from a wineskin.

The excavation, at the beginning of the 1980s, brought to light a large rectangular room with an apse, identifiable as a nymphe- triclinium. In the apse there were the housings of the two statues recovered in 1969; within niches along the walls, there were other statues of characters linked to the family of the emperor of Claudius (his mother Antonia Minor and one of his daughters who died at an early age).
After a long work of conservation and restoration, the statues together with part of the architectural decoration are now exhibited in the Castle of Baia, in a room of the archaeological museum, in a suggestive almost life-size reconstruction of the submerged Nymphaeum. The Submerged Park of Baia now allows visitors, through two guided tours, to enjoy and enhance what the sea inexorably covered two thousand years ago.