One of the ways in which Tamburlaine the Great invites comparison to epic poems is its meticulous attention to and cataloging of the nations, cities, and terrain of the world it describes. Unlike Homer with Ancient Greece, however, Marlowe had no firsthand knowledge whatsoever of the regions of Northern Africa, the Middle East, and southeastern Europe in which his play takes place.
Most of Marlowe's audiences probably would've had only the vaguest idea of where the places his characters name stood in relation to one another, but there's evidence that Marlowe actually did quite meticulous research in order to try to get the cartography of Tamburlaine's world right. To a modern reader, once one has figured out which archaic names refer to which modern-day locations, Marlowe's geography seems deeply confused and confusing. It's unfair, however, to judge Marlowe by our modern standards. When there are mistakes in his geography, they're nearly always attributable to the shortcomings of the knowledge available to him, which is hardly his fault. Moreover, if we call Marlowe's geography inaccurate and leave it at that, we risk missing the deeper meaning of Marlowe's relationship to cartography and its influence on Tamburlaine.
Marlowe clearly took maps seriously enough that he had his hero call for one on his deathbed. He knew enough about them, also, to make Tamburlaine himself a knowledgeable mapmaker. During the siege of Damascus, Tamburlaine proclaims that "Here at Damascus will I make the point / That shall begin the perpendicular," which is baffling enough if you don't know the language of cartography (Pt.1.4.4.79-80). During Marlowe's time, cartographers had a range of choices for their "meridian"—the line at which the longitude of a map is 0. Meridian lines were also deeply bound up in the international politics of conquest; for example, the important Treaty of Tordesillas in 1494 divided up the newly discovered lands outside Europe—Africa, North and South America, and much of Asia—by means of a specified meridian line. But because this line was insufficiently defined and measured, the division remained contested, and the conflicts between these two mighty empires often involved cartographical disputes.
Thus maps must have looked very different to Marlowe than they do to us. Instead of stable representations of a relatively consistent world, maps in Marlowe's time were tentative stabs at capturing a world in flux, much of it as yet undiscovered or insufficiently documented, its very concept somewhat unstable—the earth had, after all, been definitively proven to be round less than 100 years before Marlowe wrote Tamburlaine. And they were also highly political—as they still are, though more subtly—when Marlowe wrote, in the early days of Europe's global imperial project. The liveliness that Marlowe saw in maps emerges in his preference for the maps of Abraham Ortelius, today less known than his friend Mercator's maps, but equally respected in Marlowe's day. Ortelius's maps (pictured below) have the further distinction of being beautiful, essentially works of art.
Looking over his maps, Tamburlaine laments "And shall I die, and this unconquerèd?" referring, of course, to regions not yet brought under his dominion. But we can imagine that to Marlowe this also referred to those parts of the world not yet brought into the dominion of human understanding. It is, after all, the human mind, ever "climbing after knowledge infinite," that Tamburlaine defines as at the core of humanity's aspirations. Marlowe sees in maps a picture of humankind's quest to "comprehend the wondrous architecture of the world," to develop a system of knowledge equal to the vastness of the world we find ourselves in. While we may have a much clearer idea today of the location of Zanzibar, we might ask ourselves whether, overall, we've really come much closer to finding for ourselves was Marlowe was seeking in his maps.
