The shape of things can be the result of many factors. But usually the European middle ages cities were roughly circular in shape as this allowed a good protected area- wall length ratio. As there certainly existed good reasons to look for shelter, cities usually were placed on higher ground when compared to the surroundings, and often right on top of a hill. Mont St Michel is the clearest example (although by size it is not a city), but there are others, as Betanzos in Spain, where just 30 m (some 90 ft) of level difference already shows the issue. In these cases, the city plan shows relations between built volumes, but far from what the real urban space can provide. To begin with, side walls become visible as buildings along the street line are on different levels, but the ground level must also adapt.
Arcades appear as one of the first devices by which urban retail areas configure a special space. A large part of the streets of the old town of Bologna, in Italy, have arcades, that today are usually a substitute for what would be conventional sidewalks. This allows pedestrians to get protection from the sun, but in winter days snow and ice can resist longer…
Arcades being a typological element, they adopt diferent shapes in the Bologna landscape, with diverse constructive solutions, but always maintaining protected paths on which urban retail can be enjoyed.
Old Bologna is almost flat, but what happens with streets on hills?
In the small Galician city of Betanzos some streets adapt the arcades to the slope towards the river.
Arcades even become a space for restaurants with a view