In this paper we present the physics of the city, a new approach in order to investigate the urban dynamics. In particular we focus on the citizens’ mobility observation and modeling. Being in principle the social dynamics not directly observable, our main idea is that observing the human mobility processes we can deduce some features and characteristics of social dynamics. We define the automata gas paradigm and we write a crowding equation able to predict, in a statistical sense, the threshold between a selforganized crowd and a chaotic one, which we interpret as the emergence of a possible panic scenario. We show also some specific results obtained on the Venezia pedestrian network. Firstly, analyzing the network we estimate the Venice complexity, secondly measuring the pedestrian flow on some bridges we find significant statistical correlations, and by the experimental data we design two different bridges flow profiles depending from the pedestrian populations. Furthermore considering a reduced portion of the city, i.e. Punta della Dogana, we build up a theoretical model via a Markov approach, with a stationary state solution. Finally implementing some individual characteristics of pedestrians, we simulate the flows finding a good agreement with the empirical distributions. We underline that these results can be the basis to construct an E-governance mobility system.