The Sudeten and Carpathian mountain ranges are located on either side of Poland's southern border. Within Poland, neither of these ranges is forbidding enough to prevent substantial habitation; the Carpathians are especially densely populated. The rugged form of the Sudeten range derives from the geological shifts that formed the later Carpathian uplift. The Carpathians in Poland, formed as a discrete topographical unit in the relatively recent Tertiary Era, are the highest mountains in the country. They are the northernmost edge of a much larger range that extends into the Czech Republic, Slovakia, Ukraine, Hungary, and Romania.