Neighbourhoods are led to construct themselves in a homogeneous way, in a sort of community in the sense of aggregated groups, not necessary only in terms of ethnicity but in terms of socio-economic characteristics. This relects migration, socio-economic difference and the dynamic of the city development. These neighbourhoods have a potential of self-regulation and stabilisation of the city that is often underestimated. Thus, I think that the mixture of a city is the result of mobility, but cannot be the starting point, in particular in modern, lexibilised societies in which weak identities search for stabilizing communities.