Book IV of Plato’s republic discusses specifically the city ‘Kallipolis’. Adeimantus begins by arguing that the ruler of the city will be unhappy, given that they are not afforded certain luxuries, such as being allowed to own property, amass any private wealth, or have a mistress. Socrates however responds to this overall argument by saying that the goal of the city is not to make any single person happy, but rather the city happy as a whole, and inso doing, making the individuals happy anyways. Socrates also argues against the use of money in a society, instead suggesting that the the rulers should insure that no one exists at any extreme end of the spectrum, because wealth inspires laziness, and poverty inspires rebellion. Adeimantus argues that this city would not be able to protect itself from outside danger and influence without money, however as usual, Socrates has an answer to that as well. [I find that Socrates spends all of his time refuting arguments, and very little time providing in-depth solutions, if any at all…]
The discussion then turns to the virtues of the city. These virtues are meant to achieve/reflect justice, and are parallel with the sense of justice within the individual, in the form of reason, spirit, and appetite. In the context of the city, they are represented by specific peoples. Wisdom is the virtue exemplified by the ruler(s), as their intricate knowledge of how the city should be run should theoretically always make for a better city. [This is also where the argument against everyone having a say comes into play] Courage is the virtue exemplified by the auxiliaries, and it is a virtue of the city because they are supposed to have the best possible outcome for the city as their sole goal. Moderation is the virtue that is represented by the producers, as a just society takes into account the good of the city above all else.
The idea of moderation is perhaps most important. Balanced and harmonious individuals are what the Kallipolis are attempting to create in the first place.