The Karoo is a semidesert natural region of South Africa. The Karoo is partly defined by its topography, geology and climate, and above all, its low rainfall, arid air, cloudless skies, and extremes of heat and cold. The Karoo is distinctivly divided into the Great Karoo and the Little Karoo by the Swartberg Mountain Range, which runs east-west, parallel to the southern coastline. The Little Karoo (also called Klein Karoo) lies to the south of the Swartberg range. Geographically, it is a 290-km-long valley, only 40–60 km wide, formed by two parallel Cape Fold Mountain ranges, the Swartberg to the north, and the continuous Langeberg-Outeniqua range to the south.