The ancient Portus Magnus of Alexandria with its sunken royal quarter was once home to historical figures Cleopatra VII and Mark Antony. Franck Goddio discusses his many years of exploration at the site and some key discoveries. Since the early 1990s Franck Goddio and the European Institute for Underwater Archaeology (IEASM), in cooperation with the Egyptian Ministry of Antiquities and the Hilti Foundation, have explored the submerged remains of the great eastern port of Alexandria, the Portus Magnus. Through painstaking survey and detailed stratigraphic excavation, an accurate map of the harbour floor has been developed and many of its important buildings revealed. These include the palaces and temples on the Island of Antirhodos and the Poseidium Peninsula where Julius Caesar, Mark Antony, and Cleopatra VII used to stay, as well as the commercial infrastructure that crowded its ports. In this lecture, Franck Goddio presents for the first time a sweeping panorama of his 25 years of work in the Portus Magnus in order to demonstrate its life history from its origins as a small Egyptian fishing village, through the subsequent foundation of the city by Alexander the Great and its years as the lavish centrepiece of the Ptolemaic empire, to its place in the Roman empire as the greatest trading emporium in the whole world. For more information about Franck Goddio and the European Institute for Underwater Archaeology (IEASM): https://www.ieasm.org/ https://www.franckgoddio.org/ https://www.youtube.com/@Franck_Goddio For more information about the OCMA: https://ocma.web.ox.ac.uk/ For more information about the Hilti Foundation: https://www.hiltifoundation.org/