… we don’t know exactly who founded the Library and we aren’t clear on precisely when. What is clear is that it was quite early in the history of what was to become the great city of Alexandria and that its establishment made the city a centre of learning for centuries to come. What should also be made clear, however, is that it was not actually a “library” that was established at all. The “Great Library” that we refer to was a collection of books associated with a religious shrine – the Musaeum or Mouseion. This institution was, as the name implies, dedicated to the Nine Muses: Clio (history), Urania (astronomy), Calliope (epic poetry and song), Euterpe (lyric song), Polyhymnia (sacred song), Erato (erotic song), Melpomene (tragedy), Thalia (comedy) and Terpsichore (dance). The temple to the Muses had a dedicated priest appointed by the Ptolemaic kings and was the centre of a complex that included an exhedra, or hall, with recesses and seats for lectures and private study. According to the only and rather brief surviving description, given by Strabo in the early first century AD, it also included a communal dining hall with kitchens, a dormitory and other residential apartments, extensive gardens decorated with statues and a shaded walk. What we call the “Great Library” was a collection of books gathered to service the scholars who were housed and worked in the Mouseion and it was stored partially in the complex itself and, later, on other sites including at least three “daughter libraries”. The popular image of the Great Library as an echoing hall lined with shelves of scrolls with desks and tables for scholars is almost certainly inaccurate. That kind of library, which is still the model for many traditionally-styled libraries today, was developed much later by the Romans and the Mouseion would instead have had “a colonnade with a line-up of rooms behind … the rooms would serve for shelving the holdings and the colonnade provide space for the readers.” (Lionel Casson, Libraries of the Ancient World, Yale University Press, 2001, p. 34)

The Mouseion at Alexandria was far from the only shrine to the Muses in the ancient world, nor was it the only one with an associated centre of study. Pythogoras had recommended the establishment of a shrine to the Muses for the promotion of learning on his first arrival on Croton, for example and the Seleucid kings built one at Antioch in the late second century BC, with an attendant centre for study and a library. The fact that the Great Library was actually associated with a religious shrine is something that is ignored or glossed over in many modern accounts. [Carl] Sagan […] mentions about how one of the “daughter libraries” was the Serapeum, which was the temple of Serapis, but he skips around this in a rather gingerly manner. He says the Serapeum was “once a temple, but was later reconsecrated to knowledge”. This is nonsense. The Serapeum was always a temple and was not “reconsecrated” to anything. Libraries were often established as adjuncts to temples but it seems Sagan was attempting to distance the “annex” of the Great Library from the temple in which it sat because this did not quite fit his theme of secular knowledge’s superiority to “mysticism”. Like the Serapeum, the Mouseion was a temple with a research institution and a book collection associated with it.

This aside, the Mouseion really was primarily a research institution and its associated book collection – which we will continue to refer to by the shorthand expression the “Great Library” – was clearly one of if not the most extensive in the ancient world (more on that below). Many famous ancient scholars worked in the Mouseion, including Eratosthenes and probably Ptolemy. But several who are often claimed as working there (or even as being “librarians” of the Great Library, no less) clearly did not. Sagan’s hymn of praise says that Hipparchus studied there, but he seems to have only used some of the books from the collection and there is no evidence he ever even visited from his home on Rhodes. Likewise Sagan says Archimedes worked there, but there is no clear evidence for this and what little we know of Archimedes’ life indicates he spent it in Syracuse. Of the others Sagan mentions, Euclid and Herophilos may have studied there, depending on when the Mouseion was established and Dionysius of Thrace is another maybe, though more likely. On the whole, Sagan’s roll call of great scholars is mainly hyperbole and speculation rather than historical fact. The other figure who is regularly invoked as being associated with the Great Library, and even presented as its “last librarian”, is (again) Hypatia. This is despite the fact that both the Great Library and its daughter library in the Serapeum had ceased to exist by her time.

Tim O’Neill, “The Great Myths 5: The Destruction Of The Great Library Of Alexandria”, History for Atheists, 2017-07-02.