12 Grimmauld Place

12 Grimmauld Place is the ancestral home of the House of Black. It is located in London, in a Muggle neighbourhood, and the location is protected by a Fidelius Charm. As the house is invisible to the neighbourhood residents, the local muggles have long since accepted the mistake in numbering which landed number 13 Grimmauld Place next to number 11.

In 1995, the home became the headquarters for the Order of the Phoenix, with consent of Sirius Black, with Albus Dumbledore becoming Secret-Keeper.

History
Number 12, Grimmauld Place was the ancestral home of the House of Black for many generations. The previous matron, Walburga Black, makes her disgust of having anyone less than Pure-Blood's in her home through the hostile shrieks of her portrait, which is affixed to the wall of the home with a Permanent Sticking Charm. The house was the home of the for decades by the Black family house-elf, Kreacher, who wandered around the building still remaining faithful to his old mistress' portrait, muttering insults about the "blood traitors" and "mudbloods" which displeased his mistress so.

Number 12, Grimmauld Place held many Black family heirlooms and posessions, such as a music box that played a sickly tune and attempted to put the listener to sleep, crested goblets, a biting silver box containing wartcap powder, and an unopenable locket which turned out to be Salazar Slytherin's Locket, one of Lord Voldemort's Horcruxes. This was where Kreacher put the object after he drove himself mad not being able to complete his master, Regulus' orders to destroy the locket due to the fact that it had to be damaged past the point of repair which was beyond the capabilities and understanding of the House-elf. Many of these Family Heirlooms were stolen and peddled by Mundungus Fletcher, including the locket which the thief was forced to give to none other than Dolores Umbridge to avoid prosecution for trading without a licence, she used to locket to enforce her Pure-Blood credentials, claiming that the 'S' stood for Selwyn a family to whome she claimed to be related (incidentally one of the Death eaters who was present when the trio escaped Xenophilius Lovegood's house was named Selwyn, suggesting that the name has much credibility).

During Sirius Black's imprisonment in Azkaban, the house was unoccupied. After his escape, Sirius gave the home over to the Order of the Phoenix to be used as a headquarters. The home required an arduous cleaning up to make it even remotely habitable. Much of this work fell to Molly Weasley and her children. The home was in such disrepair that doxies and boggarts had made themselves quite at home.

After Sirius Black was killed by Bellatrix Lestrange in 1996 during the Battle of the Department of Mysteries, the house was inherited by his godson, Harry Potter. He continued to allow the Order of the Phoenix to use it as a safehouse. After the murder of Albus Dumbledore, Grimmauld Place's Secret-Keeper in 1997, each of the members of the order to whome the secret had been imparted became Secret-Keeper's themselves, giving them the power to reveal the house to others. This unfortunealtely included Severus Snape who was believed to be on Lord Voldemort's side and therefore would allow Death Eaters into The Order's headquarters. Alastor Moody placed a number of enchantments on the house to keep Severus Snape from entering it. These were a Tongue-Tying Curse to prevent him from telling others of the place and a dust-composed form of Dumbledore, which disintegrated when the person it advanced upon said the word Kill or a variant, the point of this being that Moody believed that Snape would be too overun with guilt to say that he had killed Albus, forcing him to retreat. However Thoe Order did not know that Albus Dumbledore's death was prearranged with Severus Snape. Despite these enchantments, the Order ceased use of the house as headquarters as they still could not risk being ambushed by Death Eaters.

When Harry, Ron Weasley and Hermione Granger escaped from the Death Eater attack on Bill Weasley and Fleur Delacour's wedding ceremony in 1997, they hid at 12 Grimmauld Place. They were able to remain hidden for several months, though Death Eaters, who were staking out locations linked to The Order, skulked about the street outside, unable to see the secret location. After retrieving Salazar Slytherin's locket from Dolores Umbridge, they were forced to vacate the house after accidentally revealing its location to Yaxley when the trio tried to apparate back to Grimmauld place with Yaxley hanging on to Hermione Granger's robes. They had taken the Death Eater within the confines of the Fidelius Charm.

Etymology
The name is another of J.K. Rowling's puns: Grimmauld Place can be taken as "grim, old place" or "grim mould place."