All roads lead to (New) Rome: Byzantine astronomy and geography in a rapidly changing world

During the first few centuries CE, the centre of the known world gradually shifted from Alexandria to Constantinople. Combined with a societal shift from pagan beliefs to Christian doctrines, Antiquity gave way to the Byzantine era. While Western Europe entered an extended period of intellectual decline, Constantinople developed into a rich cultural crossroads between East and West. Yet, Byzantine scholarship in astronomy and geography continued to rely heavily on their ancient Greek heritage, and particularly on Ptolemy's Geography. Unfortunately, Ptolemy's choices for his geographic coordinate system resulted in inherent and significant distortions of and inaccuracies in maps centred on the Byzantine Empire. This comprehensive review of Byzantine geographic achievements -- supported by a review of astronomical developments pertaining to position determination on Earth -- aims to demonstrate why and how, when Constantinople fell to the Turks in 1453 and the Ottoman Empire commenced, Byzantine astronomers had become the central axis in an extensive network of Christians, Muslims and Jews. Their influence remained significant well into the Ottoman era, particularly in the context of geographical applications.