@tsarstepan,
I can see that, re primary sources.. I had some fun tracing statements or ideas from secondary source writer to writer, seeing where the kernal of a concept, or even an error, seemed to start.. My interests did cover the history of the piazzas' formation and what happened in them, but I also followed travellers' commentaries - Montaigne, for example. I'm not smart enough or rich enough to dig through early books in countries far away but I admire those who do. There was an a2ker of yore (I think it was a2k and not abuzz) named Mistral - he spent a lot of time, if I remember correctly, with old books in libraries. I think he was an amateur, but intense one, and that described me at the height of my interest. Again, if I remember right, he had walked italy tip to toe and back. My other interest re piazzas was the experiential qualities of moving through, say, tight byways into a large sunlit space, or the societal qualities of the spaces - where to conduct hangings, later named saints preaching, burnings of paintings and trinkets, horse races, dog walking, old men in overcoats convening, political protests, street markets...
Much as I researched, I never scratched the surface..