Diagon Alley (a pun on the word diagonally) is a fictional high street located in London. It is accessible to the wizarding world, to which it is something of an economic hub, but hidden from Muggles (non-magical people). However, Muggles are allowed access to it if they need to accompany their Muggle-born magical children. If a wizard or witch needs something, chances are that it can be found in Diagon Alley.
One entrance to Diagon Alley can be reached on foot by passing through The Leaky Cauldron (a wizarding pub/inn). The inn, which is invisible to Muggles, lies in between a bookshop and a music shop. To enter Diagon Alley, one must go through The Leaky Cauldron to a rear courtyard and tap a brick in the wall, found by counting three up and two across, three times. In the film, the tapping of 5 bricks around the hole in the wall opens the doorway to Diagon Alley. Given the busy nature of the area, travelling to and from Diagon Alley is likely typically done by more magical means such as Apparition or by using the Floo Network, which are both ways of wizarding transport. It contains Gringotts Bank which is run by goblins, an ice-cream parlour, pet shops, book shops, Ollivander's wand shop, magical clothing shops, broom shops, apothecaries and many others.
The DVD of Harry Potter and the Chamber of Secrets includes a video "guided tour" of Diagon Alley, apparently shot on the original film sets. In the first film, the Leaky Cauldron's entrance was filmed in Bull's Head Passage, near Leadenhall Market. In the sixth film, it was inserted into the actual Charing Cross Road, between a book store and a surveyors' storefront, while Diagon Alley's actual location was revealed to be in an alley called Cecil Court located near Leicester Square, which dates back to 1627.
The name Diagon Alley is a near homophone of the word "diagonally", which is used as a plot device when Harry mispronounces the phrase near the beginning of the Chamber of Secrets film.
Borgin & Burkes
Borgin and Burkes is an antique shop located in Knockturn Alley, containing some dubious or dangerous items such as a cursed opal necklace, or half of a vanishing cabinet set, which is used by Draco Malfoy to infiltrate Hogwarts. Lord Voldemort used to work there after he left Hogwarts during the mid-1940s. Then it was run by a certain Cataractus Burkes, though during the 1990s the only owner we ever hear of seems to be Mr. Borgin.
Eeylops Owl Emporium
Eeylops Owl Emporium sells owls and supplies such as owl treats and cages. Inside, it is dark and full of a low, soft hooting, rustling and the flickering of "jewel-bright eyes." It is here that Rubeus Hagrid purchased a snowy owl for Harry who named her Hedwig in The Philosopher's Stone.
Florean Fortescue's Ice Cream Parlour
Florean Fortescue's Ice Cream Parlour, under the management of the owner Florean Fortescue (founder and shopkeeper), sold ice cream, including sundaes, which could be enjoyed at outdoor tables. Harry spent pleasant hours here working on summer holiday assignments before his third year at Hogwarts in Prisoner of Azkaban. Mr Fortescue himself helped him with his school essays and supplied him with free sundaes every half-hour. Nearing the end of the summer holidays, Harry meets Ron and Hermione here. In the Half-Blood Prince the parlour is boarded up and Fortescue has gone missing. Rowling confirmed that Florean was murdered. Also, in the first book, when Harry goes to get his robes, Hagrid appears outside the window clutching two ice-creams." The parlour sold ice creams such as "one with chocolate and raspberry sauce with chopped nuts", which Harry eats in the first book. In the second book, Harry also buys three large "strawberry and peanut butter" cones for himself, Ron and Hermione.
Flourish & Blotts
Flourish & Blotts sells a great variety of magic books, including textbooks for Hogwarts courses and other books of general magical interest. In the back there is a corner devoted solely to divination, which includes a small table stacked with titles like Predicting the Unpredictable: Insulate Yourself against Shocks and Broken Balls: When Fortunes Turn Foul. Another small display contains the book Death Omens: What to Do When You Know the Worst is Coming.
Usually, there is a display of gold-embossed spell books the size of paving slabs in the window, but in Prisoner of Azkaban, the front window holds an iron cage filled with hundreds of copies of The Monster Book of Monsters. To deal with the vicious books, set for the third year Care of Magical Creatures class by Hagrid, the harassed manager has to gear up with thick gloves and jab at them with a knobbly walking stick, as the books tend to rip each other apart. The manager says that he had thought he had seen the worst when they bought about 200 copies of The Invisible Book of Invisibility, all of which cost a fortune and they never did find them.
In Chamber of Secrets, celebrity author Gilderoy Lockhart signs copies of his autobiography, Magical Me, at the shop the day Harry visits, from 12:30–4:30 p.m. The signing drew a huge crowd of fans (mostly middle-aged women). This is also where Lucius Malfoy slips Tom Riddle's diary into Ginny's battered old Transfiguration book, thus causing the start of the events in Chamber of Secrets.
Gringotts Wizarding Bank
Gringotts Wizarding Bank is the only known bank of the wizarding world and it is operated primarily by goblins. A snowy white building, near the intersection of Knockturn Alley and Diagon Alley, Gringotts towers over all neighbouring shops. Customers pass through a set of bronze doors and then silver ones before entering the lobby. The main floor is paved with marble and has long counters stretching along its length. Within, wizards and witches keep their money and other valuables in vaults that are protected by very complex and very strong security measures. The vaults extend for miles under London and are accessible through rough stone passageways and then by means of magic carts that travel speedily along their tracks. Gringotts also offers Muggle-Wizarding currency exchange. When Harry first visits Gringotts, he is told by Hagrid that one would have to be mad to try to rob Gringotts. Goblins are extremely greedy and will protect their money and valuables at any cost, which is the reason why they are ideal guardians for the valuables of the wizarding world. In addition, according to Hagrid, apart from Hogwarts, Gringotts is considered "the safest place in the world for anything you want to keep safe".
There are a number of methods of opening the vaults. Most vaults, such as Harry's, use small golden keys. Higher security vaults may have various enchantments or other measures upon the doors. For example, the door to Vault 713 needs to be stroked by a certified Gringotts goblin, whereupon it melts away to allow access to the contents. If anyone other than a certified Gringotts goblin touches the door, that person will be sucked into the vault, which is only checked for trapped thieves about once every 10 years. Dragons guard the especially high security vaults found in the lowest reaches of the bank, and a subterranean waterfall called the "Thief's Downfall" acts to overturn carts that pass through it and negate spells used by would-be robbers.
Gringotts Vault 713 held a small parcel wrapped in paper, inside of which was the Philosopher's Stone. Dumbledore sent Hagrid to retrieve it while he escorted Harry. Later that same day, Professor Quirrell broke into the vault under orders from Voldemort. Although he was unsuccessful in obtaining the Philosopher's Stone, the break-in shocked the wizarding world because it was unheard of for Gringotts to be robbed. Griphook claims that the protection had been lessened due to the Vault being emptied. In Deathly Hallows, Harry, Ron, and Hermione, aided by a reluctant Griphook, break into the vault of Bellatrix Lestrange where a Horcrux of Voldemort (Hufflepuff's Cup) is hidden. However, when they enter Bellatrix's vault, which is stocked with all manner of treasures, they discover that the treasure has had Gemino and Flagrante charms placed on it, which, respectively, cause any item to multiply rapidly and go red-hot whenever it is touched. The trio escape with the Horcrux by freeing a half-blind dragon that was part of the security for the vault, and clambering onto its back.
While Gringotts is largely staffed by goblins, including Griphook and Ragnok, it is known that the bank has human employees, though not apparently for banking and accounting services. Bill Weasley worked as a curse-breaker for Gringotts in Egypt, retrieving artefacts from ancient Egyptian tombs and pyramids. Fleur Delacour took a part-time job with Gringotts after participating in the Triwizard Tournament, apparently to improve her English skills, and Wizard guards are mentioned in Deathly Hallows during the break in.
The Leaky Cauldron
The Leaky Cauldron is a dark, shabby pub and inn for wizards, located on the Muggle street of Charing Cross Road in London, offering food, drinks and rooms to rent. It was founded by Daisy Dodderidge (1467–1555) in 1500 "to serve as a gateway between the non-wizarding world and Diagon Alley." The current barman and innkeeper is a wizard named Tom.
On the main floor, the inn has a bar, several private parlour rooms, and a large dining room. On the upper floors, there are a number of rooms available; Harry has stayed in Room 11, which has a talking mirror and windows that allow him to look out onto Charing Cross Road. People often stay at The Leaky Cauldron when they come up to London on shopping trips.
The pub serves as a way of entering into Diagon Alley from the Muggle world for Muggle-borns and their parents (both of whom, until the first letter from Hogwarts, have no magical knowledge or means of entering). The rear of The Leaky Cauldron opens onto a chilly little courtyard where a brick (found by counting three up and two across from a dustbin) is tapped three times.
Madam Malkin's Robes for All Occasions
Madam Malkin's is a clothing shop next to Flourish & Blotts. It sells robes and other clothing, including the standard Hogwarts-required plain black work robes, and dress robes. Madam Malkin, a squat witch who wears mauve robes, and her assistants will tailor the robes to fit right in her shop. Malkin is an archaic term for a crotchety old woman.
Harry has two meetings with Draco in Madam Malkin's shop. This is where Harry meets the first wizard of his own age, Malfoy, for the very first time in Philosopher's Stone. Harry is rather bewildered by the questions Draco asks, because Harry is still unfamiliar with many aspects of the wizarding world. A second meeting occurs just before the beginning of Harry's sixth year, in Half-Blood Prince. This meeting is far more unpleasant, and escalates quickly into a near-duel before Draco and his mother leave in disgust that Hermione would shop there.
Hagrid can never fit in here, so the first time he brought him there, he bought some ice creams while waiting for Harry.
Magical Menagerie
The Magical Menagerie is a magical creature shop that in addition to selling magical creatures also offers advice on animal care and health. The shop is very cramped, noisy and smelly, due to every inch being covered with cages. Among the creatures in the Magical Menagerie are enormous purple toads, a firecrab, poisonous orange snails, a fat white rabbit that can turn into a silk top hat and back, cats of every colour, ravens, puffskeins, and a cage of sleek black rats that play skipping games with their tails.
When Harry, Ron, and Hermione visit in Prisoner of Azkaban, a witch wearing heavy black spectacles helps them. Ron buys Rat Tonic for his pet rat Scabbers, while Hermione buys herself a cat, Crookshanks. Crookshanks had apparently been in there for a very long time, because no one wanted him and he often caused chaos in the shop.
Ollivanders
Ollivanders is a fine wands shop described as "narrow and shabby, with a sign that reads Ollivanders: Makers of Fine Wands since 382 BC in peeling gold letters over the door. The only display in the window overlooking Diagon Alley is a single wand lying on a faded purple cushion in the dusty window. Within, there are countless narrow boxes piled neatly right up to the ceiling and a spindly-legged chair" (Hagrid, however, breaks it after he sits upon it).
Mr. Ollivander, the pale-eyed, white-haired shopkeeper, makes and sells magic wands to witches and wizards as they enter school or break their old wands. He remembers every wand he has ever sold. To determine the best wand for a witch or wizard, Mr Ollivander measures various body parts (including, in Harry's case, between his nostrils) and then checks the reactions of various wands to the buyer, a process to which he refers as "the wand choosing the wizard."
The shop closed when Mr Ollivander went missing in Half-Blood Prince when Voldemort ordered his Death Eaters to kidnap Ollivander to attempt to discover more about the link between his own and Harry's wand. One of his last customers was Neville, for whom he made a wand of cherry and unicorn hair. However, Harry rescues Ollivander in Deathly Hallows.
Potage's Cauldron Shop
Potage's Cauldron Shop sells different varieties and sizes of cauldrons, including copper, brass, pewter, silver, self-stirring, collapsible, and solid gold, according to a sign outside the shop in Philosopher's Stone. Hogwarts requires its students to have a size 2 pewter cauldron (as listed in the Philosopher's Stone book list). Hagrid talked Harry out of buying a solid gold cauldron. The Cauldron Shop is very near to the entrance from The Leaky Cauldron.
Quality Quidditch Supplies
Quality Quidditch Supplies sells broomsticks and Quidditch-related items. The store windows often draw young customers to gaze longingly at the merchandise. Its most famous items on display are the Nimbus 2000 and the Firebolt broomsticks, both of which Harry would eventually own. He spent the summer before his third year gazing at the brand new Firebolt racing broom in the display window. The price is allegedly so large that it is only given upon request, though as Harry never asked, the price is unknown. Ron had previously longed for a full set of Chudley Cannons robes offered at the shop.
Slug and Jiggers Apothecary
The Apothecary sells scales, potions and potion ingredients. The shop is quite fascinating despite its very bad smell (a mixture of bad eggs and rotten cabbage). The inside includes barrels of slimy stuff on the floor, jars of herbs, dried roots and bright powders on the shelves, and bundles of feathers, strings of fangs and snarled claws hanging from the ceiling. Harry regularly buys ingredients, as well as his scales, from the Apothecary. Some of the ingredients available are silver unicorn horns (for twenty-one Galleons each), glittery-black beetle eyes (five Knuts a scoop), Dragon liver(seventeen Sickles an ounce).
Gambol and Japes
Gambol and Japes is a wizarding joke shop. It is briefly mentioned in Chamber of Secrets, where Fred, George and Lee Jordan stock up on "Dr Filibuster's Fabulous Wet-Start, No-Heat Fireworks."
Stalls
As well as many shops, Diagon Alley also contains small stalls. These stalls sell a wide range of things; including magical sweets. In Half-Blood Prince, many witches and wizards try to take advantage of the fear created by Voldemort's return. They set up stalls selling amulets and other objects, which (according to them) protect you against werewolves, Dementors and Inferi. These "dark magic protection" stalls, however, are illegal, and likely scams. Arthur Weasley is the one in charge of arresting their owners.
Wiseacre's Wizarding Equipment
Sells all sorts of equipment used in the wizard world. Harry buys his first telescope here.
Twilfitt and Tatting's
Twilfitt and Tatting's is a wizarding clothing shop located in Diagon Alley, mentioned in Half-Blood Prince by Narcissa Malfoy, who claims she would shop there rather than shopping in Madam Malkin's due to the presence of Harry, Ron, and Hermione.
Weasleys' Wizard Wheezes
Weasleys' Wizard Wheezes is a popular joke shop that started as a small school business created by Fred and George Weasley in the fourth book. It opened its doors at Number 93 Diagon Alley in the summer of the sixth book, using Harry Potter's Triwizard Winnings as starting capital. Weasleys' Wizard Wheezes sells joke and trick items, useful novelties, and Defence Against the Dark Arts items. The front of the shop is described as a fireworks display against the muffled backdrop of the dull shops in Harry's sixth year. Some of their products are U-No-Poo, Skiving Snackboxes, trick wands, Self-Inking, Spelling checking, and Smart Answer Quills, reusable Hangmans, Daydream Charms, muggle magic tricks, Edible Dark Marks, Shield Products, Instant Darkness Powder, Decoy Detonators, joke cauldrons, Wonderwitch products, 10-second pimple vanishers, Pygmy Puffs, and more.
Fred and George started using the name "Weasleys' Wizard Wheezes" in Goblet of Fire for a mail order business selling merchandise, including sweets to help students skip classes. To run their own joke shop had always been their life's ambition—an ambition they were able to realise when Harry gave them his Triwizard Tournament winnings of 1,000 Galleons. After an early departure from Hogwarts in Order of the Phoenix, the two Weasleys set up their shop in Diagon Alley, which quickly became a huge success.
Weasleys' Wizard Wheezes had to be temporarily shut down in Deathly Hallows, because the Death Eaters were keeping an eye on all the Weasleys, but Fred and George continued to run an Owl-Order service.
(Source Wikipedia)