How will the role of the European city change within the global community? Roberto Mainardi has tried to answer this question by continuing his work on the analysis of the urban system. Starting from the concept of an urban network, he examines the city as a junction of networks and gives an overall view of the most important historical urban models, in particular the metropolis and the «city-island». These explanatory models help us to understand the transformation of urban geography in Europe as compared with the evolution in North America, where the global continental market was already set up in the early years of the twentieth century. The changes in the geography of air transportation are now a significant indicator and show a resemblance and an integration between the most urbanized regions in the world.