Also known as the republic itself, Plato's imaginary city has been a source of fascination for both philosophers and authors since the book was written. Part of the reason it has such wide appeal is that Plato fuses both intensely complex and radical philosophical ideals with some seriously imaginative and creative world making. So, in order to do justice (pun totally intended) to Plato's invented city, let's review some of its major attributes:
Government: philosopher-kings called guardians
No accumulation of wealth and no private property
Women and men are educated and employed equally
No families: children are raised and educated by the state
Censorship of poetry
Serious training in warfare, but no aggressive imperialism
Every citizen has one particular profession, and they stick to that; no mid-life crises here
An elaborate and careful education in athletics, math, and music for those children who may be potential guardians
No enslavement of fellow Greeks, but non-Greek slaves are all right
Since Socrates and his pals come up with this imaginary city as a way to understand the concept of justice in individuals, Socrates draws some crucial parallels between the organization of this city and the organization of the human soul. Socrates sees the city as having three main classes of people: philosophical types (the kings), energetic and courageous types (the soldiers), and your basic, everyday worker types (everyone else).
Socrates then says that the soul is organized in the same way. There's a rational and philosophical part, an energetic part, and what he calls an "appetitive" part (which just means that it's concerned with your day-to-day biological needs and desires). Just as the city is ruled by kings, whom soldiers and citizens follow, so too should your soul be guided by reason and not by anything else. So there you go.