Baiae, named for the legendary Odysseus's helmsman, was an opulent ancient city located in what is now Campania, Italy. First mentioned by name in the second century BCE, it was known as a popular seaside resort in ancient Rome due in part to its sulfur springs and mild climate, as well as its location along the shore of what is now the Gulf of Puteoli. In her article for the BBC, Adrienne Bernhard describes Baiae as "the Las Vegas of the Roman Empire" due to the extravagance of what remains of the city: heated bathing pools, sprawling villas, and even a casino. Many famous persons of the ancient world visited or lived there, including Cicero, Virgil, Pliny the Younger, and emperors Claudius, Nero, Julius Caesar, Caesar Augustus, and Hadrian (the last of whom died there). In addition, Baiae - along with its neighboring town, Cumae - was known for hosting a sybil, or prophetess, who reportedly lived in a cave nearby and wrote the fabled Sybilline Books, which allegedly detailed the complete future of Rome. Over time, local volcanic activity belowground caused most of the remains of ancient Baiae to sink into the gulf, where they are visible today as tourist attractions. 

A brief reference to the city appears in line 32 of famous poem "Ode to the West Wind" by Percy Bysshe Shelley.

Works Cited:

Bernhard, Adrienne. “Travel - Ancient Rome's Sinful City at the Bottom of the Sea.” BBC, BBC, 5 Jan. 2018, www.bbc.com/travel/story/20180104-ancient-romes-sinful-city-at-the-botto....

Encyclopedia Britannica. 2020. Baiae | Historic Site, Italy  [online]. https://www.britannica.com/place/Baiae. Accessed 24 November 2020.

Dash, M., 2020. The Unsolved Mystery Of The Tunnels At Baiae. [online] Smithsonian Magazine. https://www.smithsonianmag.com/history/the-unsolved-mystery-of-the-tunne.... Accessed 24 November 2020.