Oxford University is a collection of colleges and academic faculties (departments) all over the city. There is no campus or central building. There are 41 colleges. The oldest colleges are Balliol (1263) and Merton (1264), the biggest is Keble, with 450 undergraduate students.
An Oxford University student chooses and then joins a college. Students live, eat and socialize in college. They also have a personal tutor in college. Students go to lectures (classes), or do academic research in faculties and department buildings.
Lake School is in the centre of Oxford, close to Worcester College, famous for its beautiful gardens and the impressive new Oxford University Business School.
Many famous people have studied and done research at Oxford University, including Sir Walter Raleigh (explorer) Alexander Fleming (Penicillin) J R Tolkein (author of The Lord of the Rings), Hugh Grant (actor) Tony Blair (former Prime Minister) and Bill Clinton (former US President). Tim Berners Lee (inventor of the World Wide Web) studied here too!
The Bodleian Library, associated with the university, is a copyright library and has a copy of every book published in the UK. Oxford University Press is also associated with the university. They printed the first book in Oxford in 1478.
You can find a lot more information about this world famous university here.