The Orientation of Maps

There is a wonderful sketch by the Uruguayan painter Joaquin Torres Garcia with a map of South America upside down.

What does it mean "upside down"?  Aren't maps horizontal projections? If they are perpendicular to the line of gravity there is no up or down, right?  So, technically speaking, any orientation would be correct, or at least not better than any other.  Still, the mapmaker has to make a decision.  Torres Garcia is absolutely deliberate in his choice, orienting the triangle of South America pointing up, in opposition to north up, pretty much the norm for the last few centuries.  He says it himself: "... our north is the South.  There must not be north, for us, except in opposition to our South.  Therefore we now turn the map upside down..."

In the Middle Ages, European world maps were drawn orienting east up.  Actually, that's where the word orientation comes from, oriens, Latin for east.  Take for example the late 13th century Hereford Mappa Mundi, a perfect circle (more than 4 feet in diameter!) surrounded by the ocean with Jerusalem at the center, Asia covering the the upper half, Europe the lower left quadrant and Africa the lower right quadrant.  "É strano ma funziona" (strange but it works) as Italians like to say.  The dark vertical strip between Europe and Africa is the Mediterranean.  The horizontal strip in the middle is the Aegean to the left--follow it and you'll find Constantinople perfectly located between Europe and Asia--and the Nile to the right.  On top, where the sun rises... paradise.  Makes sense, don't you think?

In any case, when it comes to cities, way smaller chunks of the world, maps are oriented in all sorts of ways, imperial capitals with their imperial palaces in the center or at the top, coastal cities with their coastlines at the top or the bottom, gridded cities with their grids aligned with the edges of the drawings, and in many other case-specific--and most interesting--ways.