History of Alexandria Severus after temporary abolition by Augustus. Monumental buildings were erected in Alexandria through the third century BC. The Heptastadion connected Pharos with the city and the Lighthouse of Alexandria followed soon after, as did the Serapeum, all under Ptolemy I. The Museion was built under Ptolemy II; the Serapeum expanded by Ptolemy III Euergetes; and mausolea for Alexander and the Ptolemies built under Ptolemy IV. The Ptolemies fostered the development of the Library of Alexandria and associated Musaeum into a renowned center for Hellenistic learning. Luminaries associated with the Musaeum included the geometry and number-theorist Euclid; the astronomer Hipparchus; and
Library of Alexandria largest and most significant libraries of the ancient world, but details about it are a mixture of history and legend. The earliest known surviving source of information on the founding of the Library of Alexandria is the pseudepigraphic "Letter of Aristeas", which was composed between 180 and 145 BC. The "Letter of Aristeas" claims that the Library was founded during the reign of Ptolemy I Soter ( 323– 283 BC) and that it was initially organized by Demetrius of Phalerum, a student of Aristotle who had been exiled from Athens and taken refuge in Alexandria within the Ptolemaic court. Nonetheless,