C.C.'s Spa and Resort was a "luxurious spa" run by the sorceress Circe, the immortal daughter of Hecate. In Greek mythology, it was a place where she lured men onto her island and turned them into pigs.
Percy Jackson and Annabeth Chase wash up there after the CSS Birmingham is destroyed. Circe transforms all males who arrive at the resort into guinea pigs (originally pigs, but Circe complains they were too smelly). The only known employees are Hylla and Reyna, who give Annabeth a makeover while Circe speaks with Percy alone.
After Annabeth returns Blackbeard and his pirates to their original form with Hermes' multivitamins, they run rampant throughout the resort. It is unknown what ultimately happens to the spa after they were finished with it. Percy and Annabeth escape the spa in Blackbeard's pirate ship, the boat called Queen Anne's Revenge.
Reyna tells Percy that they had met once before, but not directly. She was on Circe's island and lived there with her sister, Hylla. She saw Percy and Annabeth arrive on the island during their quest and is still slightly angry about the situation toward him and Annabeth for destroying her home. She eventually made it to Camp Jupiter and in the four years since then, she became Praetor.