The Sto Plains are the rough analogue to Western Europe on the Discworld. They are a land of rich black loam, upon which rests a great squat forest of cabbages. The cabbage has an almost mythic status among the people of the Sto Plains, and is an emblem of its largest and dominant city, Ankh-Morpork. Most young people who leave the farming areas of the Plains for life in the big city would happily never see a cabbage again.
Although they have been an empire in the past, the Sto Plains currently exist as a loose collection of independent city-states, ruled over by a close-knit (and probably interrelated) ruling class. The Sto Plains could be thought of as being similar to Germany prior to the unification of the states into the German Empire, with no overall authority. According to Mort the area was to be united in the coming decades. As reality was given a retcon in the book, the Duke who united the Sto Plains was Mort, and he did it by diplomacy rather than conquest. In Soul Music, a footnote states various facts of the region:
• Principal export: Cabbages
• Flora: Cabbages
• Fauna: Things that eat cabbages and do not mind not having any friends