Burning of the Royal Library of Alexandria engraving taken from page 578 of "Popular History of Egypt" by John Westrop Watkins, 1886. Alexandria was founded by Alexander the Great in 331 BC. The Royal Library of Alexandria was one of the largest and most significant libraries of the ancient world. It flourished under the patronage of the Ptolemaic dynasty and functioned as a major center of scholarship from its construction in the 3rd century BC until the Roman conquest of Egypt in 30 BC. With collections of works, lecture halls, meeting rooms, and gardens, the library was part of a larger research institution called the Museum of Alexandria, where many of the most famous thinkers of the ancient world studied. Most of the books were kept as papyrus scrolls, and though it is unknown how many such scrolls were housed at any given time, their combined value was incalculable. The library is famous for having been burned resulting in the loss of many scrolls and books, and has become a symbol of the destruction of cultural knowledge. Although there is a mythology of the burning of the Library at Alexandria, the library may have suffered several fires or acts of destruction over many years. Possible occasions for the partial or complete destruction of the Library of Alexandria include a fire set by Julius Caesar in 48 BC, an attack by Aurelian in the 270s AD, the decree of Coptic Pope Theophilus in 391 AD, and the decree of the second caliph Omar ibn Al-khattab in 640 AD.