I don't know Paris specifically, but but nautilusy spiral happens (in anthropology, and also biology) when new growth happens that the position closest to the

I don't know Paris specifically, but but nautilusy spiral happens (in anthropology, and also biology) when new growth happens that the position closest to the center, which is a natural goal when proximity is a desirable feature (minimized construction costs, maximize access to community, minimize outer perimeter for defense, etc)