Mortal World:
* New York City: The story primarily takes place in and around New York City, specifically:
* Manhattan: Percy's apartment, the Empire State Building, Central Park, the Metropolitan Museum of Art, the Grand Central Terminal, and various other locations.
* Long Island: Camp Half-Blood, the demigod training camp, is located on Long Island.
* Other Locations: The story also briefly touches upon:
* Las Vegas: Percy visits the city in search of clues.
* The West Coast: Percy travels to California to confront Ares.
* Greece: Percy visits Greece in a dream sequence.
Underworld:
* The Underworld: The main setting for the climax of the story, where Percy faces Hades and his forces. This includes:
* The River Styx: The river that separates the world of the living from the Underworld.
* The Fields of Asphodel: A neutral area where those who led ordinary lives reside after death.
* The River Lethe: The river of forgetfulness, where souls drink to forget their past lives.
* Hades' Palace: The palace of Hades, the god of the Underworld, where Percy fights to retrieve Zeus' lightning bolt.
The story blends the modern world with Greek mythology, creating a unique and exciting setting for Percy's adventure.