Diagon Alley, London

Diagon Alley is a cobbled wizarding alley and shopping area located in London, England behind a pub called the Leaky Cauldron.

Inside the alley is an assortment of restaurants, shops, and other sights. All items on the Hogwarts supply list can be bought at Diagon Alley. The alley is completely hidden from the Muggle world which is right outside of its boundaries. It is very large in area and essentially the centre of wizarding London. It is a popular historical theory that the oldest building in Diagon Alley is Gringotts Wizarding Bank and that the other shops grew up around it. However, there is a possibility that Ollivanders is the oldest building, records dating back to the late fourth century B.C.

Diagon Alley is accessible from Muggle London through the Leaky Cauldron, which is on Charing Cross Road, set between a bookshop and a record shop. The Muggles who pass by the inn seem to be "quite unconscious" of its existence. Knockturn Alley, a dark artefacts area, is an off shoot of Diagon Alley.

Inside the Alley is an assortment of restaurants, shops, and other sights; some even have tables out front with coloured umbrellas. Particularly during the days or weeks before school starts at Hogwarts, the location is packed with witches and wizards, though shops are open year-round as witches and wizards travel to the location for various goods. While the shops include many school-supply locations, there are also many locations important to the wizarding world, such as  Gringotts Wizarding Bank  and  Ollivanders. Diagon Alley is also the location of  Weasleys' Wizard Wheezes, established by  Fred and George Weasley  shortly after leaving  Hogwarts.

The words "Diagon" and "Alley" when pronounced together, produce the word "diagonally" which is most probably the origin of the name "Diagon Alley". When Harry mispronounced the name due to inhaling a mouthful of ash, he landed in a fireplace in nearby  Knockturn Alley.