Our planet is full of extremes; some of which have already been discovered, while some are waiting for their big moment. Right from the tallest mountain in the world to the deepest-known point of the planet, we have used almost all the superlatives known to us, to describe the wonders of the natural world. Or have we? While everybody knows about the world's deepest and longest rivers, very few people seem to know which river is the widest. World's Widest River - The Amazon Almost everybody knows that the Amazon is the largest river in the world. Its average discharge of 7,381,000 cu ft/s exceeds the average discharge of the next seven rivers put together. It also boasts of being one of the longest river in the world at 3,976 miles; second only to river Nile of Africa (4,132 miles). That again is a subject of debate with some sources putting the length of Amazon at a whopping 4,200 miles. Other than the fact that it is the largest and one of the longest rivers in the world, the Amazon also boasts of being the widest river in the world measuring a decent 7 miles at various places along its course. When we talk of 7 miles, we are talking about the width of Amazon during the dry season. In contrast, during the wet season, when the river swells and floods the Amazon forest, it has a width of around 25 miles at some places. (When the Amazon forest floor is flooded, species like the Amazon river dolphin (Inia geoffrensis) and tucuxi (Sotalia fluviatilis) are seen swimming around the trees.) The river is at its widest at its mouth where it meets the Atlantic Ocean in Brazil. At this point, the main stream of the Amazon is 50-miles wide. *The length of the Amazon fluctuates between 3,889 and 4,200 miles depending on which source you are taking into consideration. What about Río de la Plata? Many people believe that Río de la Plata of South America is the widest river in the world with a width of 140 miles at its widest point. It is difficult to believe that a river can be so wide unless you come across the funnel-shaped indentation caused by it along the southeastern coastline of South America. In the inner part, this river is a mere 1.2 miles wide, but as you move out, its width increases and reaches a maximum of 140 miles (220 km) at its mouth. The 180-mile long river forms the border between Argentina and Uruguay. The capital city of Argentina, Buenos Aires is situated on the western banks of this river. Even though it is considered a river by many people, experts are of the opinion that Río de la Plata is actually an estuary, which forms as a result of confluence of two rivers - River Uruguay and River Parana. That explains the mixture of freshwater and seawater in this water body. At the same time, scholars who specialize in the geography of this region are of the opinion that Río de la Plata is a gulf along the South American coast and therefore, shouldn't be considered the widest river. At the same time, some people even go a step further and argue that the Río de la Plata is a marginal sea of the Atlantic Ocean, which is mistaken for a river. With Río de la Plata technically being an estuary, giving it the credit of being the widest river would be nothing short of a blunder, which leaves us with the Amazon as the hands-down winner. Critics are of the opinion that those who take Río de la Plata as a river fail to take the brackish nature of water at its mouth into consideration. One also has to make a note of the fact that, saltwater being denser than freshwater tends to settle at the base and therefore, one may not even realize that saltwater exists beneath the top layer of freshwater in this water body.