Atlanta

Atlanta is the capital of and the most populous city in the US state of Georgia, with a population of around about 420,000. It is where the Georgia Aquarium is located, which is home to Phorcys and his wife and sister, Keto. The seven demigods land the Argo II near the city in The Mark of Athena.

The Mark of Athena
The seven demigods land the Argo II near the city on the summit of a forested hill. Coach Hedge says that General Sherman, a greek demigod son of Ares/Mars and a Union leader, once stood on the very same hill. Percy, Frank, and Coach Hedge then set out to find the primordial sea god, Phorcys. They find him at the Georgia Aquarium, after recieving help from a lady called Esther, a librarian at the Carter Center, who drove them personally downtown towards the Aquarium.