The southern border of Lower Silesia is mapped by the mountain ridge of the Western and Central Sudetes, which since the High Middle Ages formed the border between Polish Silesia and the historic Bohemian region of the present-day Czech Republic. The Bóbr and Kwisa rivers are considered being the original western border with the Lusatias, however, the Silesian Duchy of Żagań reached up to the Neisse river, including two villages (Pechern and Neudorf) on the western shore, which became Silesian in 1413.