Although Italian cities suffered from invasions and pillage, the urban tradition clung. Their association with the Byzantine Empire between the 6th and 9th centuries was vital, as were contacts with Islamic civilization after the 7th century, which helped kept port cities alive despite incursions. By the 11th century Italian cities were at least as vibrant as those to the north.
While urban renewal began in the port cities it was not long confined there. The Lombard and Tuscan plains were the hinterlands of Venice, Genoa, and Pisa. They were also the most fertile and productive agricultural areas in Italy.
Milan in Lombardy and Florence in Tuscany were vibrant examples of an intense interaction between city and country that fed cities both supplies and people. In the 11th and 12th centuries these cities repulsed feudal attempts at takeover.
The manorial system was designed for self-sufficiency. Market pressure hastened its demise. By the 10th century money rents were replacing tenant labor services.
Feudal lords leased or sold properties to agricultural entrepreneurs who had made their money through commerce. Manorial open fields were splintered, enclosed, and subjected to intensive cultivation by applying the same calculations of cost and revenue that accompanied business dealings.
Feudalism was overwhelmed in the cities. Some kings and lords tried to treat towns as vassals, but the exigencies of governance over wealthy merchants were beyond them. Instead, similar to ancient Greco-Roman city-states, urban centers extended their power over the surrounding countryside.
By 1300 200,000 lived in Milan, while over 100,000 each populated Florence, Genoa, and Venice. Several other Italian urban centers housed 20,000–50,000.
Meanwhile, the population of Paris was around 80,000. London was home to some 30,000. Cologne, the largest city in Germany, was about the same.
The only region comparable to northern Italy was the southern Low Countries, especially Flanders and Brabant. The population density of this region was the greatest in Europe, coupled to the most advanced and intensive agriculture, as well as hosting the predominant commercial and industrial centers.