The earliest known  world maps date to classical antiquity, the oldest examples of the 6th to 5th centuries BC still based on the flat Earth paradigm. World maps assuming a spherical Earth first appear in the Hellenistic period. The developments of Greek geography during this time, notably by Eratosthenes and Posidonius culminated in the Roman era, with Ptolemy's world map (2nd century AD), which would remain authoritative throughout the Middle Ages.