While some scenes were shot on location (like the Hogwarts Express train and Diagon Alley), Leavesden was the primary production location. The studio even built a massive set of Hogwarts castle, along with many other iconic sets like the Great Hall, Dumbledore's office, and the Forbidden Forest.
The studio is still open to the public as the Warner Bros. Studio Tour London - The Making of Harry Potter, allowing visitors to explore the sets and see behind-the-scenes props and costumes.