12 Grimmauld Place
The home of the Black family (or as they modestly prefer to call themselves, The Noble and Most Ancient House of Black) is hidden between numbers eleven and thirteen on Grimmauld Place, a twenty minute walk from King's Cross railway station in London. The street is situated around a small, shabby square and is hardly located in an idyllic area of the city: the tall houses are universally grimy and dilapidated, and many have broken windows and paint peeling from the doors. Bags of rotting rubbish lie uncollected next to front steps, infecting the air with their pungent aroma [OOTP3].
It's fair to say that Number 12 was almost certainly well cared for during the lifetime of its old owners, Orion and Walburga Black, with their House-Elf Kreacher carrying the majority of the responsibility for maintenance. Once Harry had befriended Kreacher in 1997, the latter lost no time in showing how nicely he could maintain the house when he wanted to [DH12], and so there can be no doubt that he gave his previous master and mistress the same level of service.
Following their deaths, however, the house was, to all intents and purposes, abandoned. Of Orion and Walburga's two sons, Regulus was dead and Sirius was imprisoned in Azkaban for a crime he didn't commit. Kreacher was left alone with nobody to order him around, and he simply let the house fall into disrepair. It was left empty - but for Kreacher - for a full ten years before Voldemort's return in 1995 meant that the Order of the Phoenix was reformed and needed some headquarters from which to run its operation. Number 12 Grimmauld Place, once it had been protected with a Fidelius Charm for which Albus Dumbledore was the Secret Keeper, fitted the bill perfectly [OOTP5].
The effects of a Fidelius Charm unravelling were revealed to Harry when he visited Grimmauld Place for the first time. He was informed of the secret (ie the location of the Order's headquarters) via a note from Dumbledore [OOTP3]. As soon as he read it, his perception of the street began to transform. The house began to appear bit by bit in front of him; first a worn door and then some filthy walls and windows, all of which appear to shove the two neighbouring houses aside. In a short time the entire house was there, appearing as though it had just been inflated [OOTP4].
It was at this time that the house was near its maximum state of decay. Stone steps led to a scruffy black door garnished with nothing but a knocker shaped like a coiled snake - similar to the doorknobs inside the rest of the house. There was no keyhole or letterbox. A wand tap from Remus Lupin unlocked all the latches and chains that held the door, allowing it to creak open. The entrance hall smelt of decay and was lit only by gas lamps on the walls. A chandelier and table-top candelabra, both serpent-shaped, went unused. The wallpaper was peeling, the grimy portraits were crooked on their perches, the carpet was worn, and cobwebs were strewn over everything. The hallway also featured an umbrella stand made of a troll's leg, and a curtained portrait Walburga, the second most recent resident of the house. When awakened by noise, the curtains around her portrait flew open and she began to scream insults at Order members, setting off the other pictures in the hall as well in a cacophony of screeching [OOTP4].
The Order, under the supervision of Molly Weasley, waged war on the house over the following weeks and managed to create a number of improvements in its condition, removing Doxies, huge spiders and dead Puffskeins amongst all manner of other revolting things [OOTP6]. They never managed to get rid of Walburga's portrait though, and the house was never returned to its former glory until Kreacher started to like Harry and cleaned the entire place himself [DH12].
House Layout
The full layout of the house isn't known, although a number of details have been given.
On the ground floor, there is a dining room that the Order of the Phoenix's cleaning crew attended to during the summer of 1995. They cleared the huge spiders from the dresser there, and destroyed all the china embossed with the Black family seal [OOTP6]. The portrait of Walburga is located in the entrance hall, and at the end of this, a staircase leads down to a great stone kitchen. The kitchen is mainly lit by an open cooking fire at one end of the room, and iron pots and pans hang from the arched ceiling. Members of the Order conducted their meetings here whilst the place was used as their headquarters, for which many chairs were packed into the room. During this time, people visiting or staying at 12 Grimmauld Place ate in the kitchen at a long wooden table - nobody seemed to use the dining room for this purpose, perhaps because of the spiders [OOTP5]. An old dresser held dishes, and food was kept in a pantry off one corner of the room. In the opposite corner, a door leads to the boiler room, where Kreacher the house-elf used to sleep when he lived there. He pushed filthy rags together to make a bed under the pipes, and ornamented his room with Black family photos in their smashed frames [OOTP23].
The decor doesn't improve much heading upstairs-the wall along the staircase boasts mounted house-elf heads [OOTP4]. There are several stories to the house. On the first landing there is at least one bedroom, which Hermione and Ginny shared while staying at Order headquarters, and the drawing room. The drawing room has a high ceiling, olive green walls and dark green curtains. At one end of the room is a fireplace, with cabinets on either side [OOTP6]. These cabinets were emptied of dark objects during the Order's stay at the house: items such as bewitching music boxes, biting snuffboxes, and other Black family heirlooms were all removed [OOTP6]. They couldn't shift the Black Family Tree, however, which was stuck to the wall with a Permanent Sticking Charm [OOTP6]. There was also at least one armchair, and a writing desk which once had a Boggart hiding in it [OOTP9]. At Christmas whilst the Order were using it, the drawing room was brightened by a Christmas tree glittering with fairies, which also served to block out the Family Tree [OOTP23].
Harry and Ron slept on the second story in a room with two twin beds. The room also had a wardrobe and a bin which devoured any rubbish thrown into it and then burped. Phineas Nigellus, Sirius Black's great-great-grandfather, lurked behind the frame of a seemingly vacant canvas on the wall. Here, too, the wallpaper was peeling and the carpet and blankets moth-eaten. The floorboards on the second floor were particularly creaky, which served as a convenient warning whenever Harry and Ron were having illicit discussions and were trying to avoid Mrs. Weasley's checking up on them [OOTP6].
The number of floors above the second isn't clear. The top floor consists of two rooms only, which belonged to Sirius and Regulus when they lived there [DH10]. This may be the third floor, which would give the house 4 storeys overall, or 5 if you include the basement kitchen. During the Order's occupation of the house, however, Sirius kept Buckbeak in his mother's old room, the location of which was only ever described as "up" [OOTP9]: this may therefore have been on the first or second floor, or on an additional one in between the second floor and the top floor. Also, it was revealed that Fred and George slept on a floor somewhere above Harry and Ron's room [OOTP4]. If the third floor was the top floor, it follows that they must have been in Regulus' room (assuming that Sirius slept in his own old room).
However, given that the top floor (which after all must have the same floor space as the other floors) consists of only two rooms, it is reasonable to assume that the other floors don't have very many more. Therefore, for there to be enough bedrooms to have housed the rest of the Order (Lupin, Arthur and Molly), along with Buckbeak in Walburga's old room, an extra floor seems to be the most likely option, thus giving the house an impressive 5 above-ground floors overall. This puts Sirius' and Regulus' rooms on the fourth floor; Buckbeak, Fred and George on the third; Harry and Ron on the second; Hermione, Ginny and the drawing room on the first; the dining room on the ground floor; and the kitchen in the basement. There was also a toilet that was inhabited by a Ghoul on one of the upper floors [OOTP6].
And on top of all that, there is a dusty attic at the top of the house, where Kreacher claimed to have hidden over the Christmas holiday when he had in fact been sneaking out to deliver Order secrets to Narcissa [OOTP24].
Twelve Grimmauld Place was in the Black family for years, but with the death of Sirius - the last of the Blacks - its ownership finally had to move outside the family. A few weeks after Sirius's death, his will surfaced. Unsurprisingly, Sirius bequeathed all of his earthly possession, including Number Twelve, to Harry [HBP3]. Along with inheriting the house, Harry also inherited Kreacher, who begrudgingly had to accept Harry's orders, although he looked at Harry with the deepest sense of loathing when he did it. Kreacher was ordered to relocate to Hogwarts and work in the kitchens with the other House-Elves.
Once it had been confirmed that the house really belonged to Harry rather than any of the other Black family members (such as Bellatrix), the Order continued to use it as Headquarters for another year. After Dumbledore's death, however, they were forced to relocate to The Burrow. Dumbledore was the Secret Keeper for the Fidelius Charm on Grimmauld Place, and his death resulted in each person that he had told becoming Secret Keepers instead. As this group of people included Severus Snape (assumed at this point to be a traitor), the decision was taken to move, and Grimmauld Place became empty once again [DH6].
This situation didn't last for long, however. Following Voldemort taking over the Ministry and the subsequent attack on Bill and Fleur's wedding, Harry, Ron and Hermione suddenly found themselves in London in desperate need of somewhere to stay. Despite the possibility of running into Snape, they chose Grimmauld Place [DH9]. As it happened (due mainly to the fact that Snape wasn't a traitor at all and so the security of the building hadn't really been breached), the trio weren't bother by anyone whilst they stayed in the house, until Yaxley managed to Side-Along Apparate after them on their way back from the Ministry [DH13].
Whilst they were there, Harry took the opportunity of exploring a little further, going to Sirius' and Regulus' old rooms for the first time. Sirius' was decked out in the colours of Gryffindor (mainly, no doubt, to annoy his staunchly Slytherin parents), and contained a large number of posters of Muggle motorbikes and Muggle girls in bikinis. Regulus', by contrast, was made out in homage to Slytherin and Voldemort, with clippings about the latter making up a collage on the wall that was left in place even though Regulus later rebelled against his old hero. The most interesting part of Regulus' room as far as Harry was concerned, however, was the door. It bore the sign "Do Not Enter Without the Express Permission of Regulus Arcturus Black" - revealing to Harry in an instant the identity of the mysterious RAB, and setting in motion the trail of events that led him to the Locket Horcrux [DH10].
These events happened at the start of August, and one of the first effects was that Kreacher and Harry became friends. By September the house was gleaming, as clean as it had been in Orion and Walburga's pomp [DH12]. What became of it after Harry, Ron and Hermione went on the run is unknown, however. It is also unknown what happened to it following the fall of Voldemort and the end of the Second War, but it seems unlikely that Harry and Ginny chose to live and raise their family there.