The Río de la Plata translates as the "Silver River". Most locals joke that it is anything but silver....it's more brown. The river was not named for its color but for the riches that early Spanish explorers thought would be at the end of the river.
Rio de la Plata is the 290 km long estuary formed from the combination of the Uruguay River and the Parana River. Where the rivers join it is 48 km wide, increasing to 220 km wide where it opens on the Atlantic Ocean.
The mud and silt-filled river water has coffee-brown colour and it's not good for swimming. The riverside is nice for walking though and looking at this gigantic river. I've never seen a river that wide and that brown(!!!) before.
Buenos Aires, has lots of Art Galleries, Theatres, (It helps, of course if you speak Spanish). Great parks, many bookstores, 'Porteños' are avid readers. La Boca and San Telmo are great neighboorhoods to walk around, and listen to some great Tango music. The area, around the Delta of the Rio de la Plata is a great place for walking around and picnics.
This is a huge river with Uruguay on the other side.
The color is due to red earth swept by the far tributaries that flow into the river.