To deconstruct a map, said Brian Harley, it is necessary to read between the lines and to place the cartographic facts within a specific cultural perspective. He used the ideas of literary critics to make historians of cartography aware that there is more to maps than initially meets the eye and that ‘facts’ are rarely what they first appear to be. By viewing a map as a product of a particular society, one can begin to understand why a map was made in the way it was, how it was used and valued, and its role in representing and transforming contemporary attitudes and perspectives. To search for the wider meaning of local maps, it is usually necessary to make inferences based on research into their backgrounds; one rarely finds documents giving explicit directions on how, and why, a map was to be drawn and decorated. If, as in many past studies in the history of cartography, maps are taken at face value, they can leave many of their secrets unrevealed and, indeed, can easily be misinterpreted.