The ideal Renaissance city is designed as a star-shaped fortress, where the streets and squares are organized to speed the movement of people and soldiers. Symmetry and accessibility represent the key features for the organization of the urban space. The resulting city is hierarchized and does not always guarantee an optimal degree of connectivity. Taking the baton from the work done by space syntax in the definition of properties of spatial graph representation, we introduce a method to compute urban graphs from the Euclidean representation, the corresponding line graph and the contraction of nodes with the same urban function. We analyze the urban graphs of five historic cities: Vitry le François, Avola, Neuf Brisach, Grammichele and Palmanova and compare the analysis restults with the corresponding results from space syntax. Analysis of the spectral gap and the relative asymmetry distribution show a similar structure for these cities. The irregular or reticular housing structure seems to ensure connectivity and accessibility more than the regular grids. However connectivity is ensured by the most peripheral streets, which in the space syntax representation play a marginal role.The idea of city has undergone, over time, a slow transformation reflecting the way we design, build and live the urban fabric. The primitive city, the space that starts when "the trails become roads" [26], was little more than a cluster of houses within a defensive palisade; the founding rituals of the city, however, established its sacredness, and the rituals that made the agglomerate an inherently sacred space made it possible to locate, in the core of the city, spaces for pastoral rituals, of primitive derivation, and for ceremonial games.The urban space assumed different meanings according to different founders and different cultures. The oikistic literature set in the late Roman period, from Plutarch to Procopius of Caesarea, was intended to compare the space of the sacred cities of antiquity with that of secularized cities of their contemporaneity, in which the concept of city was increasingly as that of "citizenship".The crime of "usurpation of citizenship", defined as the system of laws and rights which Roman citizens could enjoy within the state territory, was punished with death, and the granting of citizenship was used through numerous laws by emperors as instrument of loyalty-building of war allies. The extension of the rules on citizenship, along with the increasingly absolutist control by the emperor, led primarily to a substantial uselessness of the institution-privilege of "citizenship" and the impoverishment of its archaic and religious meanings, and in the second instance contributed significantly to the crisis of the empire in the fourth century.From the city made up of men narrated by Thucydides [16] we come to the city made up of streets, more and more assimilating town planning to the description of places connected by roads, through the removal of the ritual identification process of the house as a city and vice v...
