• The Rio de la Plata or River Plate forms part of the border between Argentina and Uruguay. The cities of Buenos Aires and Montevideo are located on its western and northern shores, respectively. • The Orinoco River flows through Venezuela and Colombia and is the fourth largest river in the world by discharge volume of water. • The Purus river is a tributary of Amazon and flows through Peru and Brazil. • The Madeira river flows through Bolivia and Brazil and is the biggest tributary of the Amazon.