I have little expertise in Medieval Cities and have little input, but thought it was interesting:
Cities in the Arab world were on average much larger than those in Europe, and the size of the “primate” city – the megapolis such as Baghdad, Damascus, Cairo or Istanbul – was much bigger; a fact that is indicative of a predatory state and low trade openness. Europe, on the other hand, developed a very dense urban system, with relatively small principle cities. Big cities in Europe were quite often located near the sea, being able to optimally profit from long-distance trade, whereas the largest cities in the Arab world were almost all inland.
The sociologist Max Weber introduced a distinction between ‘consumer cities’ and ‘producer cities’. Using this classification, Arab cities were – much more than their European counterparts – consumer cities.
The classical consumer city is a centre of government and military protection or occupation, which supplies services – administration, protection – in return for taxes, land rent and non-market transactions. Such cities are intimately linked to the state in which they are embedded. The flowering of the state and the expansion of its territory and population tend to produce urban growth, in particular that of the capital city.
In Europe cities are instead much closer to being producer cities. The primary basis of the producer city is the production and exchange of goods and commercial services with the city’s hinterland and other cities. The links that such cities have with the state are typically much weaker since the cities have their own economic bases. It is this aspect that accounts for the fact that Arab cities suffered heavily with the breakdown of the Abbasid Empire, while European cities continued to flourish despite political turmoil.
Between 1000 and 1300 Europe acquired an urban system dominated by typical producer cities, which prospered in spite of Europe’s political fragmentation. In fact, this fragmentation was strongly enhanced by the rise of independent communes – city-states, or cities with a large degree of local authority – which form the core of the political system of Europe’s urban belt stretching from Northern Italy to the Low Countries. Indeed, we still find this pattern in the so-called ‘Hot Banana’ – the industrial agglomeration that stretches from the southern UK to the Netherlands, through Germany and down to northern Italy.