Sea in culture of barbarian invaders and knowledge of geography took a backward step. In the seventh century, Isidore of Seville produced a "wheel map" in which Asia, Africa and Europe were arranged like segments in an orange, separated by the "Mare Mediterranean", "Nilus" and "Tanais" and surrounded by "Oceanus". It was not until the fifteenth century that Ptolemy's maps were used again and Henry the Navigator of Portugal initiated ocean exploration and maritime research. Encouraged by him, Portuguese navigators explored, mapped and charted the west coast of Africa and the Eastern Atlantic and this knowledge prepared the way for the great voyages
Geography of Asia first historian whose works are extant, who relies on earlier geography now missing except for fragments. Asia is defined by two akrai, "bluffs" or "shores." One runs from Phasis in Colchis (Georgia) at the eastern end of the Black Sea around the coast of Asia Minor to Phoenicia. The second runs from Phoenicia to the Red Sea (the ancient Red Sea comprised also the Persian Gulf and the Indian Ocean) and from there to India, after which "no man can say what sort of region it is." Asia is equal to its shores, which also define Europe and Libya. The