To the west of the Sto Plains lies the Circle Sea and Klatch. To the east lie the Ramtop Mountains. The River Ankh has its source in the Ramtop Mountains and flows west through the Sto Plains gathering silt and eventually running (or rather crawling) through Ankh-Morpork before eventually joining the Circle Sea. The Smarl River, too, has its source in the Ramtops, but has a more southerly route, keeping to the foot of the hilly mountain ranges before winding north and into the Circle Sea.
Towns & Villages
Within the Sto Plains there are also a number of smaller towns and villages:
The Sto Plains are largely composed of plains, with significant cabbage fields around and sweeping west from Ankh-Morpork. There is forest dotted throughout (and in much larger amounts to the south, before the hilly mountain range there). The Morpork Mountains are a bit southwest of Ankh-Morpork, the Carrack Mountains are east of it--a ways before the Ramtops area--and Skund Forest starts at the south end of the Carracks. Beaches and cliffs divide it from the Circle Sea.
The principle language of the Sto Plains is Morporkian. However Ankh-Morpork is famously very cosmopolitan and is home to natives of most of the lands of the Discworld and has speakers of many languages within its walls.
The legal tender in the Sto Plains is the Ankh-Morpork Dollar.