In "The Just City" a city was created by the time-traveling goddess Athena on the island of Thera prior to its Iron Age volcanic destruction. It was then populated by philosophers and children from all ages of human history and organized on the principles of Plato's "Republic", which turned out not to work so well in practice. In "The Philosopher Kings" the single original city had split into a dozen: five feuding ones on Thera and another eight on other islands where it was discovered that the inhabitants were preaching Christianity to Iron Age Greeks. In large part because of the anachronistic introduction of Christianity, all of the cities were relocated by Zeus to an uninhabited far-off planet in the 26th century, which the cities' inhabitants promptly named Plato.