The foundation of Rome on April 21, 753 BC on the Palatine remains a historical fact of capital importance in the human history, as it is the attempt to create a laboratory of integration in the political form of the 'city', in which from the founding statute itself the aim was not to place one community above the others (as in other historical realities of Mediterranean antiquity), but to build a Roman people (populus Romanus) that was in no way characterized by ethnic or (so to speak, in the modern sense) nationalistic ties. The principle is, instead, the political-voluntarist one of uniting, with the dream of building a single people, a common law, an open society. And it is precisely in the effort not to betray the original pact between the founding groups that Rome was able to create a ius civile as a fundamental law common of the new Roman citizenship, with respect to a complex legal reality of differentiated customs of the various original gentes and then of those who gradually came to be part of the community of Rome.