The sovereign state of Bolivia is a constitutionally unitary state, divided into nine departments. Its geography varies from the peaks of the Andes in the West, to the Eastern Lowlands, situated within the Amazon basin. It is bordered to the north and east by Brazil, to the southeast by Paraguay, to the south by Argentina, to the southwest by Chile, and to the northwest by Peru. One-third of the country is within the Andean mountain range. With of area, Bolivia is the fifth largest country in South America, after Brazil, Argentina, Peru, and Colombia (and alongside Paraguay, one of the only two landlocked countries in the Americas), the 27th largest in the world, the largest landlocked country in the Southern Hemisphere and the world's seventh largest landlocked country, after Kazakhstan, Mongolia, Chad, Niger, Mali and Ethiopia.