Rossem
During the days of the Galactic Empire, it was used as a political prison, and housed a small naval garrison and an observatory (Second Foundation). After the fall of the Empire, it was conquered by the "Oligarchy of Tazenda", which levied taxes to be paid in foodstuffs, brought to the village of Gentri where the governor lived ("gentry" refers to an upper class). During his search for the Second Foundation, the Mule's soldiers, Bail Channis and Han Pritcher, came to Rossem. The Mule, meanwhile, destroyed Tazenda, assuming it was the Second Foundation. He assumed incorrectly, and was defeated by the First Speaker of the Second Foundation.
Rossem was exceptionally cold, and was thus barren with a low population, exclusively in the equatorial regions. It may be loosely based on Russia in Tsarist times, which Asimov's family came from, or even specifically Siberia.
Read more about this topic: List Of Foundation Universe Planets