The Balkan mountains run laterally through the middle of the country from west to east. The mountainous southwest has two distinct alpine type ranges - Rila and Pirin, which border the lower but more extensive Rhodope Mountains to the east, and various medium altitude mountains to west, northwest and south, like Vitosha, Osogovo and Belasitsa. Musala, at , is the highest point in both Bulgaria and the Balkan peninsula. The Black Sea coast is the country's lowest point. Plains occupy about one third of the territory, while plateaux and hills occupy 41%. Most rivers are short and with low water levels. The longest river located solely in Bulgarian territory, the Iskar, has a length of . The Struma and the Maritsa are two major rivers in the south.