A conceptual diagram of the world, with a T-shape within an O creating three parts which represent the three continents, i.e. Europe, Asia and Africa. The O represented the ocean surrounding the world. The perpendicular bar of the T represented the Mediterranean, while the lateral bar represented the river Nile, separating Asia and Africa and the River Dnieper separating Europe and Asia. -
Cf. Mappa mundi
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.