The suspicion that certain ancient authorities possessed good knowledge of the real shape of the Atlantic and its islands, and of the lands on both sides of it, must also arise from any objective reading of Plato's world-famous account of Atlantis. [...], this story is set around 11,600 years ago -- a date that coincides with a peak episode of global flooding at the end of the Ice Age. The story tells us that 'the island of Atlantis was swallowed up by the sea and vanished', that this took place in 'a single dreadful day and night' and that the event was accompanied by earthquakes and floods that were experienced as far away as the eastern Mediterranean. But of more immediate interest to us here is what Plato has to say about the geographical situation in the Atlantic immediately the flood that destroyed Atlantis: 'In those days the Atlantic was navigable. There was an island opposite the strait [the Strait of Gibraltar] which you [the Greeks] call the Pillars of Heracles, an island larger than Libya and Asia combined; from it travellers could in those days reach the other islands, and from them . For the sea within the strait we are talking about [i.e. the Mediterranean] is like a lake with a narrow entrance; the outer ocean is the real ocean and the land which entirely surrounds it is properly termed continent ... On this land of Atlantis had arisen a powerful and remarkable dynasty of kings who ruled the whole island; and many other islands as well, and parts of the continent ...' Whether or not one believes than an island called Atlantis ever existed in the Atlantic Ocean, Plato's clear references to an 'opposite continent' on the far side of it are geographical knowledge out of place in time. It is hard to read in these references anything other than an allusion to the Americas, and yet historians assure us that the Americas were unknown in Plato's time and remained 'undiscovered' (except for a few inconsequential Viking voyages) until Colombus in 1492.