The manse is a five story mansion near Gramercy Park. It also doubles as a school for witchcraft.
History
In the early Twentieth Century, Hecate opened her house as a school for promising witches. However, the students started fighting amongst themselves after the outbreak of World War One. Hecate refused to intervene as she felt the students had to choose their own paths. The goddess’s decision forced her to close the school due to the student's fighting. Shortly after, the house started to crumble as its spirit slowly started to lose its will to exist.
The Senior Year Adventures
Wrath of the Triple Goddess
Hecate asks Percy Jackson to stay at her house for a week as she takes part in a ceremony to honor her. The son of Poseidon is aided by Annabeth Chase and Grover Underwood. A day after the goddess leaves, Grover drinks a potion that causes him to transform and go on a rampage, partially destroying the manse and letting Hecuba and Gale escape. Over the next few days, the three track down the pets and think of ways to fix the manse. Annabeth suggests they use Hecate's Torches to summon the ghost of Peter Stuyvesant and other deceased New Yorkers to repair the manse in a night. They choose to go with the daughter of Athena's plan and it works. However they fail to return the ghosts to their graves and the dead attack the manse. The group tries desperately to defend it until the campers find Camp Half-Blood arrive and helps defend the manse. The demigods and their allies send the ghosts back to the afterlife and they celebrate a Halloween party. After Hecate returns, Percy reveals the truth about what happened and that the house was slowly falling apart due to the goddess's loneliness. He convinces Hecate to reopen her school and they spend the weekend discussing the prospect.