T-O maps are maps of the World typical of the period from the 6th -12th centuries. They are so called because of their structure: with the East on top--"oriented"-- they are in the form of a circle with a T in the lower half of the map, with the upright being the Mediterranian Sea the left-hand bar representing the Black Sea, and the right-hand bar, the Nile River. In the center is Jerusalem, and in the uttermost East, the Garden of Eden. Sometimes a red line in the South will serve for the Red Sea; beyond this is a place marked vaguely "southern lands", whose attribution is also sketchy. (Madagascar? Antarctica? Australia? Sudan?) Small islands around the edges represent Ireland, England/Scotland/Wales, and some other, less identifiable features. Straits are shown as large rivers, and mountain ranges as wing-like shapes cutting into the Eurasian landmass. Utterly unusable as navigational aids (the southern coast of the Mediterranian is represented as a straight line), they nonetheless served for many generations the only representation of the world available to the best scholars in Europe.

Philosophically, the map makes sense in the Medieval scheme of things: the Four Elements are represented in their places in harmony, the Fiery South, the cool, earthy North, full of mountains, the watery West, and the windy East, beyond which is Paradise. This map regained some prominence when Umberto Eco used it as the basis for the coded rooms of the Aedificum in The Name of the Rose.

For those (such as myself) with poor visualization abilities who have trouble following teleny's excellent writeup, may I present an ASCII sketch:

              _.-"-._
            .'       `.
           /  A S I A  \
          |             |
Black Sea +------J------+ Red Sea
          |  EUR | AFR  |
           \ OPE | ICA /
            `._  |  _.'
               `-+-'
                 M
                 e
                 d
                 i
                 t
                 e
                 r
                 r
                 a
                 n
                 e
                 a
                 n

(Where the J in the centre is Jerusalem.)

---

T-O maps are interesting because they demonstrate how much the design of contemporary maps is arbitrary:

Firstly, as geographic information decreased proportionally to the distance from the (Arabian) mapmakers, it was natural to put the most important local city, Jerusalem, in the centre*. A similar bias may be evident in the contemporary popularity of the Mercator projection, which enlarges the temperate areas of importance to Western civilization, rather than the supposedly egalitarian Peters projection.

Modern cartography is driven first and foremost by the power of maps to control resources. Since this ability was not fully realised when T-O maps were produced, there is less emphasis on spatial correctness. (Plus, without the ability to calculate longitude, maps aren't all that useful for navigation.) Instead, these maps emphasise logical ordering which is of greater importance for general and political education. (Who is next to whom is more important than the abstract absolute position of any particular geographic entity.)

Finally, as compasses were not yet widely available, the contemporary habit of North-oriented maps is absent. Instead, mythology concerning what lay beyond the edge of the maps dictated the orientation.

---

* Interestingly enough, Avalon-Hill's History of the World game also puts the Middle East at the centre of the board and uses a projection that compresses space proportional to the distance from the edge. Presumably this is because the Middle East is not only the birthplace of civilization but also decisive events in the history of the world tend to occur closer to there than any other point.