Baia is a Roman town on the northwest shore of Naples, Italy. Due to volcanic activities, the lower part of the town sunk into the Mediterranean sea in the fourth century AD. Towards the end of the Roman Republic, it became a popular city. Several emperors such as Julius Caesar, Nero and Hadrian had villas there dating back to the 1st and 2nd centuries AD. Today, it is possible to visit the ruins by scuba diving.