I figured that, since I've been writing so much about Hypatia of Alexandria lately, it might be a good idea to give you more information on the establishment where she taught and studied: the Library of Alexandria!
The Library of Alexandria was the largest institution of its kind in the ancient world, containing 500,000 written works (some accounts even put this figure higher, at around a million volumes!). Ptolemaic rulers added to its collection by borrowing scrolls from the libraries of Rhodes and Athens and never returning them. Additionally, ships entering the city's harbor had any manuscripts they were carrying confiscated and brought to the Library to be copied and stored. This practice, and the fact that the Library's contents were so well looked-after, ensured that as the centuries passed the works in the Library of Alexandria ended up being the only surviving copies in existence.
Connected to the Library was the Museum, a center of learning dedicated to the Muses. This is where Hypatia and her father Theon would have worked and lectured. Some other great minds who studied at the Library of Alexandria included Archimedes, who discovered measurement by water displacement; Heron, who invented a method to calculate the area of polygons (ever had to use "Heron's Formula" in math class? Yeah, that's his!); Eratosthenes, who correctly calculated the circumference of the Earth; Herophilus, the so-called "father of anatomy" who identified the brain as the controlling organ of the body; and Euclid, the mathematician who was the first to prove the Pythagorean Theorem and discovered the existence of irrational numbers.
Over the hundreds of years of its existence, the Library was destroyed and rebuilt many times. For instance, in 48 B.C., a naval battle in Alexandria's harbor involving Julius Caesar inadvertently caused the Library to catch fire, destroying most of its contents. Similarly, the destruction of the Serapeum in 391 C.E. (depicted in the movie Agora) aided in reducing the Library's collection further. The final destruction of the Library of Alexandria occurred around 640 C.E., credited to the armies of Caliph Omar of Damascus. When questioned as to what to do with the Library's collection, the Islamic ruler said that the manuscripts "will either contradict the Koran, in which case they are heresy, or they will agree with it, so they are superfluous." Thousands of scrolls were then seized and burned as fuel in Alexandria's bathhouses. Sadly, because of incidents like these, much of the knowledge of the ancient world has been lost to us: we can only be thankful for the information about the Library and its intellectual community that has survived to the present day!