The Antipodes (literally "opposite feet": the place on the globe directly opposite to where you are standing)* fascinated the Middle Ages for both philosophical and geographical reasons. On the one hand, the idea had come to them from the Classical World, and so was difficult to dismiss. This was the place that held creatures out of legend: Cyclopes, dog-headed men, Sciopods whose single large foot could be used as an umbrella when they lay on their backs, Blemmyae with faces on their torsos. On the other hand, the Medieval idea of symmetry demanded that there be lands to the far south, balancing the known lands in the north. Especially as the idea of earth's roundness took shape, Africa wasn't enough to satisfactorily balance Europe and Asia.
The Antipodes were also a natural extension of the theory of "zones." Since it became very cold up north, and hotter as you went south, it was assumed that the temperate zone enjoyed by most of Europe had a counterpart below the equator which was equally inhabitable. Below that, of course would be the area that is opposite the Arctic: the Anti-Arctic, or Antarctic.
Yonde in Ethiopia ben the Antipodes, men that haue theyr fete ayenst our fete.Some in the Middle Ages used the image of upside-down men as a reason to reject the Earth as a globe and opt for a flat Earth. Plato had addressed this himself, however, in an assumption of orientation that he does not call gravity but that works the same way:
(Yonder in Ethiopia are the Antipodes, men that have their fete against our feet.)
For if there were any solid body in equipoise at the centre of the universe, there would be nothing to draw it to this extreme rather than to that, for they are all perfectly similar; and if a person were to go round the world in a circle, he would often, when standing at the antipodes of his former position, speak of the same point as above and below; for, as I was saying just now, to speak of the whole which is in the form of a globe as having one part above and another below is not like a sensible man.But sensible men apparently did not read the Timaeus, or never grasped the concept of "up" and "down" being relative to where you were standing. A universally accepted map of the world was unknown; maps of the world typically took one of four forms, which we will look at tomorrow.
*Have fun finding your antipodal point here.