Complex sentence: They had closed courts and the characteristics of the farms on the plains north of Milan, where the yard was intended to link functions and had a central role in the agricultural processing (as happened for example in the Po-valley companies).
Split into simpler sentences: They had closed courts and shared architectural characteristics of farms on the plains north of Milan. In such designs the yard was intended to functionally link the property, having a central role in the agricultural chain of production (as occurred in Po-valley companies).