At its most basic, the Greek concept of the continents was a rough division of the known world into 3 equal parts. The border between Europa and Asia was at the Hellespont. The border between Europa and Libya (which we call Africa) was the Mediterranean.

In this view, everything roughly north and/or west of what is now the Bosporus and Dardanelles was Europe. This included the lands of the Celts in Iberia and the regions north of it. It also included Skythia, which as a geographical region covers a large area including modern Ukraine, south-west Russia and Kazakhstan. It did not, however, include the Greek cities on the western coast of what is now Turkey; these people were habitually referred to as "the Greeks in Asia." It also did not include Carthage, which was in Libya.

There was, however, certainly a political dimension to the continents too, in the sense that Europa was represented (quite unrealistically) as a land ruled by the Greeks, whereas Asia was the domain of the Persians. The Persian King's claim to supreme power in Asia is repeated in several Greek sources as legitimate, if not simply a fact of life. This did, however, allow for the border between Asia and Europe to become somewhat fuzzy, since the actual extent of Persian control over Asia Minor shifted over time.

There was also a cultural dimension to the division of the world into continents. We first see this in Herodotos' account of a dream that Xerxes supposedly had, in which he tried to yoke two women to his chariot; the women were personifications of Europe and Asia (both names are conveniently feminine in the Greek), and the dream was a metaphor for Xerxes' attempt to add Europe to his Empire. The woman representing Asia quietly accepted the yoke, but the one representing Europe, tall, fair and defiant, refused it.

This is one of the early pieces of evidence we have for what we now call Orientalism - the tendency of European cultures to stereotype those of Asia as more docile, prone to subservience and cowardice, and ruled by cruel and perverted despots. This negative stereotype is of course intended to be contrasted with a Europe that is proudly independent, freedom-loving and ambitious. Already the Classical Greeks indulged to a great extent in such generalisations, characterising Asia (including the areas settled by Greeks) as mostly a "soft" land, producing weak peoples destined to be ruled by others. Europe, to their mind, was a tougher mistress, and therefore bred men destined to rule.

Modern scholars recognise that a lot of these stereotypes were born at the time of the Persian Wars, when the Greeks first began to see themselves as a single people with a culture quite distinct from those of their Eastern neighbours. In this way, the ripples caused by Xerxes' failed invasion still stir the waters of modern history.