There is no single "Hogwarts Castle" in real life; instead, the filmmakers used a combination of real-world locations, studio sets, and a massive 1:24 scale model. The most iconic real-world locations include Alnwick Castle in Northumberland, where the broomstick flying lessons were filmed, and Durham Cathedral, which provided the backdrop for various hallways and the transfiguration classroom. The University of Oxford played a major role, with the Bodleian Library serving as the Hogwarts library and the Christ Church Dining Hall providing the architectural inspiration for the Great Hall (though the hall itself was a set built at Leavesden Studios). Gloucester Cathedral and Lacock Abbey were used for many of the dark, stone cloisters and corridors seen throughout the films. For wide shots of the entire castle, the crew used an incredibly detailed miniature model that can now be seen at the Warner Bros. Studio Tour London - The Making of Harry Potter. This model was used for every film in the series and was digitally enhanced to create the majestic, sprawling castle seen on the big screen.