The Royal Library of Alexandria, or Ancient Library of Alexandria, in Alexandria, Egypt, was probably the largest, and certainly the most famous, of the libraries of the ancient world. It flourished under the patronage of the Ptolemaic dynasty, and functioned as a major center of scholarship, at least until the time of Rome's conquest of Egypt, and probably for many centuries thereafter. Generally thought to have been founded at the beginning of the third century BC, the library was conceived and opened either during the reign of Ptolemy I Soter or during the reign of his son Ptolemy II. Plutarch (AD 46120) wrote that during his visit to Alexandria in 48 BC, Julius Caesar might have accidentally burned the library when he set fire to his own ships to frustrate Achillas' attempt to limit his ability to communicate by sea. According to Plutarch's account, this fire spread to the docks and then to the library. However, this version of events is not confirmed in contemporary accounts of Caesar's visit. In fact, it has been reasonably established that segments of its collection were partially destroyed on several occasions before and after the first century BC. A modern myth (no older than the late eighteenth century) attributes the destruction to Coptic Christian Archbishop Theophilus of Alexandria in 391, who called for the destruction of the Serapeum; but in fact there was no connection between the library and the Serapeum and some historians of late antiquity do not take the claim seriously. Another version of the story, not recorded till the thirteenth century, blames the Muslim sacking of Alexandria in 642.