Final answer:
The Paraná River is the river that forms the confluence of the Paranaíba and Grande Rivers in southern Brazil and is later joined by the Iguazu River. This occurs near the Triple Frontier, where Brazil, Paraguay, and Argentina meet.
Step-by-step explanation:
The Paraná River forms the confluence of the Paranaíba, and Grande Rivers, in southern Brazil, which is subsequently joined by the Iguaçu River. This joining of rivers occurs near the Triple Frontier, where Brazil, Paraguay, and Argentina meet. The Iguazu Falls, close to the confluence, is an incredible natural attraction about 1.7 miles along its edge and features a series of 275 parallel waterfalls almost two miles across, with the highest being 269 feet.