the southeastern coastline of South America. Depending on the geographer, the Río de la Plata may be considered a river, an estuary, a gulf, or a marginal sea. If considered a river, it is the widest in the world, with a maximum width of 220 km.

The river is about 290 km long and widens from about 2 km at its source to about 220 km at its mouth. It forms part of the border between