The eastern, southern and western plains in Uruguay eventually flow into the rolling hills and low mountains of the interior. In the southwest, the flat lowlands between the coastline and hills (Littoral) merge more gradually into the hilly interior.
Along the Atlantic, near Montevideo, sandy beaches ring the coastline. In the east - from Punta del Este to Cabo Polonio - the coastal plain is sandy, marshy, and broken by a few bays and lagoons.
In the north, a series of low mountains run north into the highlands of Brazil. In the east, a narrow band of low mountains extends from the coastal areas through Treinta y Tres.
In this land of rivers, major ones include the Uruguay, which flows south along its entire border with Argentina, on into the River Plate (Rio de la Plata; the Negro, and the Yi (its largest tributary); the Cebollati, and the Yaguaron on the border with Brazil.
Formed by dams on the Negro, a huge artificial lake extends across the center of the country.