The Bodleian Library is a collection of 26 libraries spread across Oxford, including the central University library. It houses over 13 million items, ranging from books and journals to rare manuscripts and archives.
There's a number of tour options, from 30 minutes to 90 minutes. You can check them out here! I'd recommend the 30-minute tour that covers both the Divinity School and Duke Humfrey’s Library. Note that only kids 11 years old and up can do the tour. If you can't do a tour, it's worth walking by the outside of the Radcliffe Camera for pictures!
Filming: Bodleian Library was the infirmary in four of the Harry Potter movies. It was also used when Harry went into Hogwarts’ library undetected due to his invisibility cloak! Visit the Duke Humfrey’s Library, the oldest reading room in the Bodleian Library for this scene.