Mount Tamalpais

Mount Tamalpais is located on the outskirts of San Francisco and is the location of the Garden of the Hesperides, as well as the site where Mount Othrys is being rebuilt by the Titans as a war base during the Battle of Manhattan while Kronos, the Titan Lord of Time, is assaulting Manhattan so he can get to Mount Olympus which is atop the Empire State Building. It is named the Mountain of Despair and happens to also be the sight where Atlas holds up the sky. Both ordinary mist and Mist are very thick on the mountain. Many monsters are attracted to it. The mountain is close to where Annabeth's dad and his family live. Annabeth stayed there for the summer, saying she was able to keep watch.

The Titan's Curse


Percy, Annabeth and Zoe travelled here to save Artemis and, if need be, Annabeth, from Luke and the Titan Army's grasps. It is noted that the mountain smells like Eucalyptus because dragons like to chew it. Here, they fought Zoe's father, the Titan General Atlas until they pinned him under the sky.

The Battle of the Labyrinth
Percy, Annabeth, Nico di Angelo, and Rachel Elizabeth Dare, a mortal, discover a passage in the Labyrinth that leads to Mount Orthys after going back into the Labyrinth hours after the fight against Kelli the empousai cheerleader, the spirit of Minos, and some dracae in Daedalus's workshop.

The Last Olympian
Percy has a dream of this place, one of the Titan gods Atlas, Hyperion and Krios talking of the explosion of the Princess Andromeda, and of Nico spying on the Titans outside Mount Othrys.

The Lost Hero
Jason mentions that during the Second Olympian War, while the Greek Camp Half-Blood was in New York defending Mount Olympus and Manhattan against Kronos and his Titan Army during the Battle of Manhattan, the Roman demigods were fighting the Titan Krios and the remaining forces that remained here.