Mountains dominate central and western Rwanda and the country is sometimes called Pays des mille collines in French (Land of a thousand hills). They are part of the Albertine Rift Mountains that flank the Albertine branch of the East African Rift, which runs from north to south along Rwanda's western border. The highest peaks are found in the Virunga volcano chain in the northwest; this includes Mount Karisimbi, Rwanda's highest point, at . This western section of the country lies within the Albertine Rift montane forests ecoregion. It has an elevation of . The centre of the country is predominantly rolling hills, while the eastern border region consists of savanna, plains and swamps.