The face of the city is its information

What is it in the externally represented face of the city that makes it recognizable and imaginable? What makes some urban elements and artifacts more legible and better remembered than others? Or put more generally: What makes an object an external representation and what makes it better perceived and/or remembered? Our answer to all these questions is “the information they embody and convey”. Some elements, including those that compose the face of the city, are quantitatively and qualitatively more informative than others and are therefore more legible and better perceived and remembered, quantitatively, in terms of Shannon's theory of information (The Mathematical Theory of Communication, University of Illinois Press, Urbana, IL, 1949), and qualitatively in terms of Haken's (Information and Self-organization: a Macroscopic Approach to Complex Systems, Springer, Heidelberg, 1988/2000) notion of semantic information. In this paper, we elaborate on this point of view in three steps: In the first, we introduce Shannonian information and show how it can be used to define the amount of information externally represented in different urban elements. In the second, we show how this is related to processes of grouping and categorization that give meaning to the face of the city and thus form its semantic information. In the third, we discuss implications for cognition in general and for cognitive mapping in particular.