Ptolemy’s GeographyThe recovery of Ptolemy’s Geography in the early fifteenth century gave Europeans new access to ancient geographical knowledge. This 1486 world map, based on Ptolemy, is a great advance over medieval maps but contains errors with significant consequences for future exploration. It shows a single continent watered by a single ocean, with land covering three-quarters of the world’s surface. Africa and Asia are joined with Europe, making the Indian Ocean a landlocked sea and rendering the circumnavigation of Africa impossible. Australia and the Americas are nonexistent, and the continent of Asia is stretched far to the east, greatly shortening the distance from Europe to Asia via the Atlantic. (Bibliothèque nationale de France/Giraudon/The Bridgeman Art Library)