Fra Mauro's mapamundi was created before Portuguese explorers sailed around Africa, yet it shows that at least at a certain level there was a fairly precise knowledge of the world.
Between 1457 and 1459, and commissioned by king Afonso V of Portugal the Venetian monk, Fra Mauro, created a map of the world; his mapamundi,
as it became known from its description in Latin (the term means "map
of the world") is now considered by many as the finest expression of
medieval cartography. But the map isn't just an expression of art and
culture: It was done for very practical purposes that were considered
top secret and shows a level of knowledge that is far beyond what is
assumed for the late medieval period.