The evidence presented by the ancient maps appears to suggest the existence in remote times, before the rise of any of the known cultures, of a true civilization, of a comparatively advanced sort, which either was localized in one area but had worldwide commerce, or was, in a real sense, a worldwide culture. This culture, at least in some respects, may well have been more advanced than the civilizations of Egypt, Babylonia, Greece, and Rome. In astronomy, nautical science, mapmaking and possibly ship-building, it was perhaps more advanced than any state of culture before the 18th Century of the Christian Era. It was in the 18th Century that we first developed a practical means of finding longitude. It was in the 18th Century that we first accurately measured the circumference of the earth. Not until the 19th Century did we begin to send out ships for purposes of whaling or exploration into the Arctic or Antarctic Seas. The maps indicate that some ancient people may have done all these things.
Charles H. Hapgood Maps of the Ancient Sea Kings: Evidence of Advanced Civilization in the Ice Age