Athene sets up a city based on Plato's Republic and peoples it with freed slave children, worker robots, and men and women from up and down the timeline. About five years in, Socrates shows up and starts asking some difficult questions.
If you haven't read Plato, that's OK. I haven't, either, and I still understood the book.
One warning: there are a couple scenes of sexual violence, and Jo Walton doesn't shy away from it.
Now I need to read the sequels.