This map of the world, known as the Beatus map, dates to the 12th century AD. It is a variation on the medieval mappus mundi format, a depiction of the world based on the T-O design. The map hides a secret: it conceals a hidden grid.
The grid is signalled by the presence of a right-angled device on which Adam and Eve are shown standing.
The bottom of the device defines the alignment of the grid.
The height of the squares is defined by the height of the two human figures.
When these squares are sub-divided further into sixths, and extended across the full design, it is apparent that much of the text that has been added to the map adheres to the grid.
The presence of this invisible grid underlying the layout of the map points to a lost art of cartographic cryptography.
