Urban flora is a more and more interesting research subject, in light of the ongoing environmental change and biological homogenisation, since urban contexts are much more diversified that natural ones and, therefore, they offer much more colonisation possibilities to allochthonous species or unexpected refuges for endangered species. We have, therefore, added our own contribution by analysing the spontaneous vascular flora of 7 cities of the Emilia-Romagna Po Plain (northern Italy), one of the more culturally and economically developed areas in Europe. The global floristic list was 1305 species, spanning from 432 to 756 species in each individual city; 219 of them were constantly present in all cities examined. A notable richness in phytosociological classes (43 out of 75 known for the entire national territory) was observed. Therophytes were 35.4% of the spectrum, followed by hemicryptophytes, phanerophytes and geophytes. Eurasian and Mediterranean species dominated (average values 30 and 27%, respectively); exotic species were 26.8%, in line with the strong floristic pollution of Emilia-Romagna, with neophytes always prevailing over archaeophytes. Among neophytes, 44.8% came from the Americas and 26.2% from Asia. Some hydro-hygrophilous and halophilous species were found, owing to the presence of watercourses crossing the urban areas and coastal wetlands bordering one of the towns. The species new for the flora of Italy or Emilia-Romagna were 32, of which 24 were allochthonous. The species protected at a regional or national level were hardly present, which is normal in artificial environments. Despite the inevitable differences in exploration intensity and effort, this synthesis offers a picture of the contribution given by anthropogenic habitats to the global biological richness of the territory.