The Uruguay River forms the border between Uruguay & Argentina & most of the border between Argentina & this country
However, the falls are not visible for 150 days per year and become 
more... [DOC] [TLE] Ro de la Plata - Wikipedia [PAR] The Ro de la Plata rendered River Plate in British English and the 
Commonwealth and La Plata River (occasionally Plata River) in other English-
speaking countries  is the river and estuary formed by the confluence of the 
Uruguay ...