Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is also the world's fifth-largest country by area and the seventh-largest by population, with over 213 million people. The country is a federation composed of 26 states and a Federal District, which hosts the capital, Brasília. Its most populous city is São Paulo, followed by Rio de Janeiro. Brazil has the most Portuguese speakers in the world and is the only country in the Americas where Portuguese is an official language. Bounded by the Atlantic Ocean on the east, Brazil has a coastline of 7,491 kilometers (4,655 mi). Covering roughly half of South America's land area, it borders all other countries and territories on the continent except Ecuador and Chile. Brazil encompasses a wide range of tropical and subtropical landscapes, as well as wetlands, savannas, plateaus, and low mountains. It contains most of the Amazon basin, including the world's largest river system and most extensive virgin tropical forest. Brazil has diverse wildlife, a variety of ecological systems, and extensive natural resources spanning numerous protected habitats.