The Sub-Balkan valleys include nine valleys, situated between the Balkan Mountains in the north and Vitosha and Sredna Gora in the south. With an area of 1,186 km2 and an average altitude of 550 m, Sofia Valley is the largest of the nine and contains the nation's capital, Sofia. The Rose Valley encompasses the valleys of Karlovo and Kazanlak and is renowned for its rose-growing industry, which has been thriving there for centuries, producing 85% of the world's rose oil. The Kazanlak Valley is also known as the Valley of the Thracian Kings due to the extremely high concentration and variety of monuments of the Thracian culture.