Shaping ideal cities: the graph representation of the urban utopia

摘要

The ideal Renaissance city is designed as a star-shaped fortress, where thestreets and squares are organized to speed the movement of people and soldiers.Symmetry and accessibility represent the key features for the organization ofthe urban space. The resulting city is hierarchized and does not alwaysguarantee an optimal degree of connectivity. Taking the baton from the workdone by space syntax in the definition of properties of spatial graphrepresentation, we introduce a method to compute urban graphs from theEuclidean representation, the corresponding line graph and the contraction ofnodes with the same urban function. We analyze the urban graphs of fivehistoric cities: Vitry le Fran\c{c}ois, Avola, Neuf Brisach, Grammichele andPalmanova and compare the analysis restults with the corresponding results fromspace syntax. Analysis of the spectral gap and the relative asymmetrydistribution show a similar structure for these cities. The irregular orreticular housing structure seems to ensure connectivity and accessibility morethan the regular grids. However connectivity is ensured by the most peripheralstreets, which in the space syntax representation play a marginal role.