Mont St Michel, France. Image from Wikipedia
Mont St Michel, France. OSM map
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.
Betanzos, as seen on the city website http://www.betanzos.net
metrhispanic 