Number 12, Grimmauld Place

• Type: Residence, Headquarters
• Location: Borough of Islington, London, England
• Owner/Residents: The Black family (formerly); Sirius Black (by inheritance); Harry Potter (by inheritance). Notable temporary residents include Albus Dumbledore, Kreacher, and various members of the Order of the Phoenix, including Ron Weasley, Hermione Granger, the Weasley family, Nymphadora Tonks, and Remus Lupin.
• Key Features: Unplottable; protected by a Fidelius Charm; magically concealed between two Muggle houses; filled with Dark Arts artifacts and malevolent enchantments; features the Black family tapestry.

Number 12, Grimmauld Place is the ancestral home of the Black family, a wealthy and ancient pure-blood wizarding family with a fanatical devotion to blood purity. The house itself is a reflection of the family's dark history: it is a gloomy, dilapidated Georgian terraced house located in a shabby part of London. For generations, it housed the Black lineage until the death of its last traditionalist matriarch, Walburga Black. After her death, and with her son Sirius Black imprisoned in Azkaban, the house fell into deep decay, inhabited only by the family's loyal but mentally unstable house-elf, Kreacher. The house is magically hidden from Muggles and unauthorized wizards. It is squeezed between numbers 11 and 13 and will only become visible to a person if the Secret-Keeper of its Fidelius Charm has personally revealed the location to them. The exterior is grimy and unkempt, with peeling paint and dirty windows. The interior is equally grim and oppressive. The decor is dominated by serpentine motifs, and the entire house is permeated by a feeling of coldness and neglect. It is infested with various magical pests like Doxies and contains numerous dangerous artifacts. Notable features include a foul-tempered, life-sized portrait of Walburga Black in the entrance hall which screams insults at visitors, a macabre display of severed house-elf heads mounted on plaques, and a troll's leg umbrella stand. Upon his escape from Azkaban, Sirius Black offered his family home to Albus Dumbledore to serve as the headquarters for the reconstituted Order of the Phoenix. Members of the Order, along with the Weasley family, undertook a major effort to clean and decontaminate the house, though many of its dark enchantments and artifacts proved difficult or impossible to remove.

Grimmauld Place serves as a crucial location in the second half of the series. In Harry Potter and the Order of the Phoenix, the house is the central hub for the Order of the Phoenix and is where Harry Potter spends the latter part of his summer after the Dementor attack in Little Whinging. It is a place of both refuge and frustration for Harry, as he feels isolated and kept in the dark by Dumbledore and the Order. Many key Order meetings and strategic discussions occur here. It is also from here that Harry has a vision of Arthur Weasley being attacked by Nagini at the Ministry of Magic. In Harry Potter and the Half-Blood Prince, Harry inherits the house and all its contents, including Kreacher, following the death of Sirius Black. He visits briefly to confirm his ownership and test Kreacher's allegiance before returning to the Dursleys. In Harry Potter and the Deathly Hallows, Number 12 becomes a primary sanctuary for Harry Potter, Ron Weasley, and Hermione Granger after they escape from the attack at Bill Weasley and Fleur Delacour's wedding. They use it as a base while planning their hunt for Lord Voldemort's Horcruxes. It is here that they uncover the story of Regulus Arcturus Black and his betrayal of the Dark Lord, realizing that Kreacher holds vital information about the real locket Horcrux. The trio's use of the house as a safe haven ends abruptly when the Death Eater Yaxley grabs hold of Hermione Granger during her Apparition away from the Ministry of Magic, thereby being brought within the bounds of the Fidelius Charm and compromising its location forever.

• Entrance Hall: A long, high-ceilinged hall, dark and cavernous. It contains the screaming portrait of Walburga Black, the troll's leg umbrella stand, and the wall of mounted house-elf heads.
• Basement Kitchen: A large, shadowy room with rough stone walls and a large fireplace. This serves as the main meeting and dining area for the Order members. It contains a long wooden table and a cupboard where Kreacher sleeps.
• Drawing Room: Located on the first floor, this room has an air of faded grandeur. It is notable for containing the vast Black family tapestry, which shows the family tree. Sirius Black had burned his own name off the tapestry. The room was infested with Doxies and contained a writing desk in which a Boggart was found.
• Sirius Black's Bedroom: Located on the second floor, Sirius's room was a clear act of rebellion against his family's values. The walls were covered with Gryffindor banners and permanent sticking charms were used to affix pictures of Muggle girls in bikinis and motorcycles.
• Regulus Black's Bedroom: A smaller bedroom decorated with Slytherin colors and banners. It contained newspaper clippings about Lord Voldemort and was where the trio found the locket replica and the note from R.A.B.
• Other Bedrooms: Several other gloomy bedrooms were used by Harry, Ron, Hermione, Ginny Weasley, and other Order members during their stays. One contained a wardrobe that housed a Boggart.

• The name “Grimmauld Place” is a pun on the phrase “grim old place,” which accurately describes the house's decaying and depressing atmosphere.
• After the death of Albus Dumbledore, the original Secret-Keeper, a magical loophole in the Fidelius Charm made it so that everyone to whom he had revealed the secret became a Secret-Keeper themselves. This allowed over a dozen people to know the location, increasing the risk of discovery.
• In the film adaptations, the house is shown to magically push the adjacent Muggle houses aside to reveal itself, a visual effect not explicitly described in the books (film). The set design for the interior heavily emphasized the dark, dusty, and neglected state of the house, particularly the Black family tapestry, which was a major set piece (film).