Westover Hall is a military academy in Bar Harbor, Maine where Grover Underwood discovered two demigods, Bianca di Angelo and Nico di Angelo. The principal was Ms. Gottschalk and the vice principal was Dr. Thorn. A rescue party - consisting of Percy Jackson, Thalia Grace, and Annabeth Chase - was sent to extract Grover and the new demigods, Nico and Bianca Di Angelo, undercover during a school dance.
Westover Hall looks like a castle where an evil knight would live, according to Percy: all black stone, with towers and slit windows. A big set of wooden doors on the edge of a rocky, snowy unwelcoming cliff overlooking a big frosty forest at one side and a gray churning ocean on the other. The inside is decorated with antique war paraphernalia: battle flags, old rifles, and medieval weapons. According to Percy, the female students were quite wild. Groups of them roamed on dance floor occasionally surrounding an individual male, planting ribbons in his hair and leaving lipstick prints all over his face.
- Nico di Angelo (no longer attending due to the realization of being a demigod)
- Bianca di Angelo (no longer attending due to the realization of being a demigod)
- Grover Underwood (no longer attending due to finishing his assignment to get Nico and Bianca di Angelo to safety)
- Percy Jackson (thought to be a student by Mrs. Gottschalk due to the Mist)
- Annabeth Chase (thought to be a student by Mrs. Gottschalk due to the Mist)
- Thalia Grace (thought to be a student by Mrs. Gottschalk due to the Mist)
|Magical Locations:||Aeolia | Camp Half-Blood (Grove of Dodona) | Camp Jupiter | Cave of Trophonius | C.C.'s Spa and Resort | Daedalus' Workshop | Lotus Hotel and Casino | Mount Othrys | Ogygia | Olympus | Pan's Cave | Sea of Monsters | The Labyrinth | Tartarus | Underworld | Waystation|
|Cities, States, and Towns:||Alaska | Bar Harbor | Bologna | Chicago | Detroit | Gila Claw | Indianapolis | Jamestown | Long Island | New Mexico | New York City (Manhattan) | Quebec | San Francisco | Dalmatia (Split) | Vancouver | Venice | Westport|
|Other Locations:||Apennine Mountains | Aunty Em's Gnome Emporium | Carlsbad Caverns | Crusty's Water Bed Palace | Empire State Building | Gateway Arch | Grand Canyon | Greece | Hoover Dam | Italy | Junkyard of the Gods | Mount Diablo | Mount Etna | Mount Saint Helens | Mount Tamalpais | Pikes Peak | Polyphemus' Island | ROFL | Rome | Triple G Ranch | U.S.A. | Waterland|