To have followed the speculative vision of Behaim in his famous globe, or of others like him, would have been disastrous, even though their work represents the cream of fifteenth-century mapmaking and was known to Columbus. Indeed, as one commentator has observed, if his chart had been based on the Behaim scenario, 'Columbus could not even have known of the whereabouts of the New World, much less discover it.'
Yet not only does he seem to have known where he was going but, on some accounts, when he was going to get there:
'Now and then Pinzón and Columbus consult and deliberate — mutually discuss their route. The map or chart passes not infrequently from the one captain to the other; the observations and calculations as to their position are daily recorded, their conduct and course for the night duly agreed upon.
On the eve of their due arrival Columbus issues the order to stay the course of the armada, to shorten sail, because he knew that he was close to the New World and was afraid of going ashore during the obscurity of the night ...
How does he know the place and the hour?
'His Genius' says the Columbus legend in explanation. But the Map? The critics will ask, what did it contain? Whose was it? What did that map contain that was so frequently passed from Columbus to Pinzón during the voyage?'
I've presented my case that what the map may have contained was an accurate but ancient, and indeed antediluvian, representation of the coast and islands of Central America, notably the north-south-oriented Great Bahama Bank island, which Columbus — no less ignorant than any of his contemporaries about the existence of the Americas — took to be an accurate map of part of the coast of China and the islands of Japan.

Traditions, with all their folksy redolences, are relatively safe matters for scholars to speculate about. Maps and nautical charts on the other hand — especially accurate, sophisticated maps of the kind used by Guzarate to chart Vasco da Gama's course from Malindi to Calicut in 1498 — are quite another matter. If maps have indeed come down to us containing recognizable representations of Ice Age topography — as arguably may be the case with the depictions of India and of the long-submerged Sundaland peninsula by Cantino and Reinal and with the depiction of the 'Golden Chersonese' by Ptolemy — then prehistory cannot be as it has hitherto been presented to us.
If they are what they seem, such maps mean a lost civilization. Nothing more. Nothing less.

If the normal portolano is indeed derived from the lost atlas of Marinus of Tyre, then it follows that other high-quality maps of regions much further afield than the Mediterranean and the Black Sea, and indeed a world map, might also have been preserved by the Arabs — for we know from Ptolemy's testimony that other Marinus maps, including a world map, did once exist. It will therefore do no harm to keep an open mind to the possibility that the portolan world maps that began to appear during the century after the Carta Pisane, might also have been influenced by earlier 'Tyrian sea-fish' maps of Phoenician origin. Christopher Columbus, whose passionate belief in lands across the Atlantic lead to his 'discovery' of the New World, seems to hint at a Phoenician connection when he describes one of the inspirations for his journey:
'Aristotle in his book On Marvellous Things reports a story that some Carthaginian merchants sailed over the Ocean Sea to a very fertile island ... this island some Portuguese showed me on their charts under the name Antilia.'
Antilia first appears on a portolan chart of 1424. It is a mysterious presence there, a riddle.

In 1512, in handwritten notes on an enigmatic map that he had prepared showing the newly discovered Americas, the Turkish Admiral Piri Reis offered an intriguing answer to all these questions — at any rate for the particular case of Christopher Colombus, the most recent and most renowned of the ancient Atlantic dreamers. Piri's note, one of many on the same map, is written over the interior of Brazil:
'Apparently a Genoese infidel, by the name of Columbus was the one who discovered these parts. This is how it happened: a book came into the hands of this Colombus from which he found out that the Western Sea [i.e. the Atlantic] has an end, in other words that there is a coast and islands on its western side with many kinds of ores and gems. Having read this book through, he recounted all these things to the Genoese elders and said, 'Come, give me two ships, and I shall go and find these places.' They said, 'Foolish man, is there an end to the Western Sea? It is filled with the mists of darkness.

Behind the maps of the sixteenth century lies another story—the change in geographical conceptions, mapmaking, and map usage that took place in the late Middle Ages. Pietro Vesconte, Cresques Abraham, Fra Mauro, Andrea Bianco, and Henricus Martellus Germanus were among the medieval cartographers who began to reshape the image of the world before Columbus sailed west.

As his ship reached the entrance to Goa harbour, on 15 December 1515, Albuquerque died just before dawn, aged sixty-three. His mark on the history of the Indian Ocean was indelible, and he had had the satisfaction of knowing that his foremost enemy, the Zamorin of Calicut, Mana Vikrama, had gone before him. He had done his best to arrange that.

[T]he designer of a unified architecture is in a similar situation as the cartographers that set out to draw the first maps of the world, based on the reports of traders and explorers returning from expeditions into uncharted waters and journeys to unknown coasts.

The ancient map of Persia, Colchis,. and Armenia is absolutely full of the most distinct and startling evidences of Indian colonization, and, what is more astonishing, practically evinces, in the most powerful manner, the truth of several main points in the two great Indian poems, the Ramayana and the Mahahharata. The whole map is positively nothing less than a journal of emigration on the most gigantic scale.

This map by cartographer Herman Moll was commissioned by the South Sea Company. The entire region displayed, with the exception of Brazil, was claimed as the company’s trading territory. Disregarded was the fact that Spain claimed the same territory.

Amongst those [works] of the tenth century, of which fragments are now extant, is a system of mineralogy by Avicenna, a physician in whose arrangement there is considerable merit. In the same century also, Omar, surnamed 'El Aalem,' or 'the Learned,' wrote a work on 'the Retreat of the Sea.' It appears that on comparing the charts of his own time with those made by the Indian and Persian astronomers two thousand years before, he had satisfied himself that important changes had taken place since the times of history in the form of the coasts of Asia, and that the extension of the sea had been greater at some former periods. He was confirmed in this opinion by the numerous salt springs and marshes in the interior of Asia,-a phenomenon from which Pallas, in more recent times, has drawn the same inference.

In that Empire, the Art of Cartography attained such Perfection that the map of a single Province occupied the entirety of a City, and the map of the Empire, the entirety of a Province. In time, those Unconscionable Maps no longer satisfied, and the Cartographers Guilds struck a Map of the Empire whose size was that of the Empire, and which coincided point for point with it. The following Generations, who were not so fond of the Study of Cartography as their Forebears had been, saw that that vast Map was Useless, and not without some Pitilessness was it, that they delivered it up to the Inclemencies of Sun and Winters. In the Deserts of the West, still today, there are Tattered Ruins of that Map, inhabited by Animals and Beggars; in all the Land there is no other Relic of the Disciplines of Geography.

The Spanish voyager, as his caravel ploughed the adjacent seas, might give full scope to his imagination, and dream that beyond the long, low margin of forest which bounded his horizon lay hid a rich harvest for some future conqueror; perhaps a second Mexico with its royal palace and sacred pyramids, or another Cuzco with its temple of the Sun, encircled with a frieze of gold. Haunted by such visions, the ocean chivalry of Spain could not long stand idle.

The earth’s round, like an orange, but this map is like its skin, cut off in ovals, north to south, laid flat and stretched a bit at the top and bottom. A Dutchman called Mercator invented the way to do this accurately twenty years ago. It’s the first accurate world map.

There are several other sources of enjoyment in a long voyage, which are of a more reasonable nature. The map of the world ceases to be a blank; it becomes a picture full of the most varied and animated figures. Each part assumes its proper dimensions: continents are not looked at in the light of islands, or islands considered as mere specks, which are, in truth, larger than many kingdoms of Europe. Africa, or North and South America, are well-sounding names, and easily pronounced; but it is not until having sailed for weeks along small portions of their shores, that one is thoroughly convinced what vast spaces on our immense world these names imply.