 Both Porto Alegre, the capital and most populous city of Rio Grande do Sul, and Viamão lies on its eastern shore.The cities of Guaíba, Eldorado do Sul and Barra do Ribeiro lies opposite to Porto Alegre, on the western shore.The Lake Guaíba is navigable, and is connected to the Atlantic Ocean through Lagoa dos Patos and its outlet channel, located farther south, at the city of Rio Grande.