Hogwarts School of Witchcraft and Wizardry, is a fictional British school of magic for students aged eleven to eighteen. Hogwarts is somewhere in Scotlan. The school is depicted as having numerous charms and spells on and around it that make it impossible for a Muggle to locate it. Muggles cannot see the school; rather, they see only ruins and several warnings of danger. The castle's setting has extensive grounds with sloping lawns, flowerbeds and vegetable patches, a loch (called The Black Lake), a large dense forest (called the Forbidden Forest), several greenhouses and other outbuildings, and a full-size Quidditch pitch. There is also an owlery, which houses all the owls owned by the school and those owned by students. Some rooms in the school tend to "move around", and so do the stairs in the grand staircase. Witches and wizards cannot Apparate or Disapparate in Hogwarts grounds, except when the Headmaster lifts the enchantment, whether only in certain areas or for the entire campus, so as to make the school less vulnerable when it serves the headmaster to allow Apparition.[GF Ch.28] Electricity and electronic devices are not found at Hogwarts. In Harry Potter and the Goblet of Fire, Hermione indicates that due to the high levels of magic, "substitutes for magic (that) Muggles use" such as computers, radar and electricity "go haywire" around Hogwarts. Radios however, make an exception. The radios are not powered by electricity but by magic.
Hogwarts is on the shore of a lake, sometimes called the Black Lake. In that lake are merpeople, Grindylows, and a giant squid. The giant squid does not attack humans and sometimes acts as a lifeguard when students are in the lake.
Admission to Hogwarts is selective, in that children who show magical ability will automatically gain a place, and squibs cannot attend the school as students (though they can work there in other roles, as Argus Filch does). A magical quill at Hogwarts detects the birth of magical children and writes their names into a large parchment book, but there is no admission test because "you are either magical or you are not." Every year, a teacher checks this book and sends a letter to the children who are turning eleven. Acceptance or refusal of a place at Hogwarts must be posted by 31 July. The letter also contains a list of supplies like spell books, uniform, and other things that the student will need. The prospective student is expected to buy all the necessary materials, normally from shops in Diagon Alley, a concealed street near Charing Cross Road in London that can be found behind the wizarding pub, The Leaky Cauldron. Students who cannot afford their supplies can receive financial aid from the school, as happened with the young orphan Tom Riddle.
Letters to Muggle-born witches and wizards, who may not be aware of their powers and are unfamiliar with the concealed wizarding world, are delivered in person by a member of Hogwarts staff, who then explains to the parents or guardians about magical society, and reassures them regarding this news
Each student is allowed to bring an owl OR a cat OR a toad. Along with the acceptance letter, first-year students are sent a list of required equipment which includes a wand, subject books, a standard size 2 pewter cauldron, a set of brass scales, a set of glass or crystal phials, a kit of basic potion ingredients (for Potions), and a telescope (for Astronomy). The Hogwarts uniform consists of plain work robes in black, a plain black hat, a pair of protective gloves, and a black winter cloak with silver fastenings. Each uniform must contain the wearer's nametag. First years are not allowed a broomstick of their own, though an exception to this rule is made for Harry in his first year after he demonstrates an excellent ability as a Seeker in Quidditch.
Hogwarts is divided into four houses, each bearing the last name of its founder: Godric Gryffindor, Salazar Slytherin, Rowena Ravenclaw and Helga Hufflepuff. Throughout the school year, the houses compete for the House Cup, gaining and losing points based on actions such as performance in class and rule violations. The house with the highest end-of-year total wins and has its colours displayed in the Great Hall for the following school year. Each house also has its own Quidditch team that competes for the Quidditch Cup. These two competitions breed rivalries between the houses. Houses at Hogwarts are living and learning communities for their students. Each house is under the authority of one of the Hogwarts staff members. The Heads of the houses, as they are called, are in charge of giving their students important information, dealing with matters of severe punishment, and responding to emergencies in their houses, among other things. Each year, year level groups of every separate house share the same dormitory and classes. The dormitory and common room of a House are, barring rare exceptions, inaccessible to students belonging to other Houses.
In the early days of Hogwarts, the four founders hand-picked students for their Houses. When the founders worried how students would be selected after their deaths, Godric Gryffindor took his hat off and they each added knowledge to it, allowing the Sorting Hat to choose the students by judging each student's qualities and placing them in the most appropriate house. The student's own choices may affect the decision: the clearest example is the Hat telling Harry that he would do well in Slytherin in the first book, but ultimately selecting Gryffindor after Harry asks it not to put him in Slytherin.
Gryffindor values courage, bravery, nerve, and chivalry. Gryffindor's mascot is the lion, and its colours are scarlet and gold. During the books, the Head of this house is the Transfiguration Professor and Deputy Headmistress, Minerva McGonagall until she becomes headmistress, and the house ghost is Sir Nicholas de Mimsy-Porpington, more commonly known as Nearly Headless Nick. According to Rowling, Gryffindor corresponds roughly to the element of fire. The founder of the house is Godric Gryffindor.
The Gryffindor common room is in one of the castle's highest towers, and its entrance is on the seventh floor in the east wing of the castle and is guarded by a painting of The Fat Lady, who is garbed in a pink dress. She permits entry only after being given the correct password, as was established in the third book, when Sirius Black tried forcing entry into the tower, only to be blocked by The Fat Lady after he could not give the correct password. In the first book, Neville Longbottom tends to forget the password and must wait near the painting until other Gryffindors arrive to open the way.
Hufflepuff values hard work, patience, justice, and loyalty. The house mascot is the badger, and canary yellow and black are its colours. During the books, the Head of this house is the Herbology Professor Pomona Sprout, and the house ghost is The Fat Friar. The founder of this house is Helga Hufflepuff.
The entrance to the Hufflepuff dormitories and common room entrance is concealed in a pile of large barrels in an alcove in the corridor that holds the kitchen. To enter, one must tap the barrel two from the bottom in the middle of the second row in the rhythm of "Helga Hufflepuff". Unlike any other house, the Hufflepuff common room has a repelling device that douses the illegal entrant in vinegar if the wrong lid is tapped or the rhythm is wrong. The Hufflepuff common room is filled with yellow hangings and fat armchairs and it has little underground tunnels leading to the dormitories, all of which have perfectly round doors, like barrel tops.
Ravenclaw values intelligence, creativity, learning, and wit.The house mascot is an eagle and the house colours are blue and bronze (blue and grey in the films). During the books, the head of this house is the Charms teacher, Professor Filius Flitwick, and the house ghost is The Grey Lady. According to Rowling, Ravenclaw corresponds roughly to the element of air. The founder of this house is Rowena Ravenclaw.
The dormitories are in Ravenclaw Tower, on the west side of Hogwarts. The common room is round and filled with blue hangings and armchairs, has a domed ceiling painted with stars and features a replica statue of Rowena wearing her diadem. Harry also notes that Ravenclaws "have a spectacular view of the surrounding mountains". A logical riddle must be solved to gain entry, whereas the Gryffindor and Slytherin common rooms only require a password (Hufflepuffs need to tap a barrel in the rhythm of "Helga Hufflepuff"), indicating that it may be easier for those students from other houses who possess a high degree of intelligence to enter this common room than others. Professor McGonagall, the head of the Gryffindor House, solves the riddle accurately.
Slytherin values ambition, cunning, leadership, and resourcefulness; the Sorting Hat said in Harry Potter and the Philosopher's Stonethat Slytherins will do anything to get their way. The house mascot of Slytherin is the serpent, and the house colours are green and silver. During the books, the Head of House is Professor Severus Snape until the seventh book. Then, Professor Horace Slughorn, the previous Head of House, comes out of retirement, re-assuming authority after Snape becomes headmaster. The ghost of Slytherin house is The Bloody Baron. According to Rowling, Slytherin corresponds roughly to the element of water. The founder of this house is Salazar Slytherin.
The Slytherin dormitories and common room are reached by speaking a password to a patch of bare stone wall in the dungeons, which causes a hidden door to open. The Slytherin common room is a long, low, dungeon-style room, under the Hogwarts Lake, furnished with green lamps and carved armchairs. The room is described in the second book as having a greenish glow.
The Sorting Hat claims that blood purity is a factor in selecting Slytherins, although this is not mentioned until the fifth book. There is no reason to believe, however, that Muggle-born students are not sorted there, merely that pure-blooded students are more desirable to that house, as there are several examples of half-bloods in the house - such as Snape, Tom Riddle/Voldemort and Harry himself was only excluded from the house at his own insistence. In Deathly Hallows, a group of Snatchers claim that "not many Mudbloods" are sorted into Slytherin.
When believing Harry to be dead and thinking that he has final victory in his grasp, Voldemort proclaims his intention to abolish the other three houses and force all Hogwarts students into Slytherin. This design is foiled by his defeat and death, after which Slytherin becomes more diluted in its blood purity, no longer remaining the pure-blood bastion it once was.