The Castel dell’Ovo is the oldest standing fortification in Naples. The castle’s name comes from a legend about the Roman poet Virgil, who had a reputation in medieval times as a great sorcerer and predictor of the future. As early as the twelfth century there were pre-norman fortifications erected on the remains of part of the villa of the Roman general Lucio Vicinio Lucullo, later transformed into a castle by Frederick II and expanded in the Angevin period, when the fortress took the name "Egg Castle"
https://www.visitnaples.eu/en/attractions-and-places-in-naples/castles-in-naples/castel-dellovo