Oxford University, the oldest university in the UK, names its official opening date as 1201--that's when the university first stated its statutes and elected its first chancellor. For those of you who don't know, Oxford operates on the collegiate system; that is, the University itself is made up of different, academically-independent colleges. Students wishing to "go to Oxford" must apply to a specific college, as they will be a student at that college specifically, not at Oxford as a whole.
Because of this collegiate system, wherein students formerly only studied at their own college,
the college libraries throughout Oxford are effectively older than what is now the university library at Oxford, the Bodleian. (However, what with the wonders of OPACs, the materials accessible via college libraries are catalogued in the Bodleian's overarching system.)
The first university library at Oxford actually began with the donation of Duke Humfrey's library upon that mans death--this first library officially opened in 1488. Beginning in 1598, however, Thomas Bodley began to make arrangements to donate his own substantial library to the university library. It was this gift of around 14,000 items that allowed the library to reopen in 1602 under its new and lasting name.
Bodley did a lot for his library. In 1602, he hired a librarian to tend the books (the Library maintains a staff position called "Bodley's librarian" to this day). In 1605, he commissioned the creation of the first catalogue of the library's holdings. Then, in 1610, he negotiated a copyright agreement with a stationer that allowed the library to receive, free of charge, a copy of everything published in the UK. Today the Bodleian still reserves the right to a copy of everything, although they actually only receive items that they request.
Bodley's library is still kept in the room purpose-built to house it, and the books are on the shelves in the same order and fashion in which Bodley and his first librarian left them. These resources are available for reader use upon request, and according to the tour guide they do get requested. Duke Humfrey's library sits just off the Bodley Library room; his books line the shelves there, and reading tables are available for reader use as well. (Fun fact: Duke Humfrey's Library is used as the Hogwarts Library in the Harry Potter films.) Readers can sit in this or other rooms, including the reading room in the oft-pictured Radcliffe Camera building:
Today the Bodleian acquires around 5,000 new items every week. They have a total of more than 11 million items, more than half of which have to be stored off-site at least until planned expansions can be built. The end result as far as on-site book storage goes is that books have taken up pretty much every space they can. They line walls and stack in the original Bodleian Library building, and they fill high-density shelves on 11 floors of a newer library building (1933) just across the street. Because all of these library stacks are closed and readers will never be browsing the shelves, new materials are shelved in order of item receipt--really, all that matters is that the books have a definite findable location on a library shelf, not that they be in any sort of subject organisation.
To move requested items from the stacks to where they will be read by readers, the Library employs a conveyor system that runs through underground tunnels. Our tour took us along part of its path, and it really does seem fantastical that the original conveyor system is still in use (albeit it will undergo enhancements soon).
Perhaps what I most like about the Bodleian, aside from its obvious beauty and history, is that the library is available to all scholars, not just Oxford students. Open accessibility was a strict requirement of Bodley for his library--he understood that knowledge is not just for a few, but for all.