It is 1320 kilometers long and has 62.000 square kilometers of basin area. It flows from the coastal Serra do Mar mountains in the Brazilian state of Paraná, near Curitiba (the capital and largest city of the state of Paraná). The river flows westward through the Brazilian Highlands, descending over nearly 70 rocky thresholds that break up its current.
Downstream from the mouth, the Iguazu forms the border between Brazil and Argentina. As it continues flowing, it descends from the plateau to form Iguazu Falls.
The Iguazu River flows into the Parana River at the point where the borders of Argentina, Brazil, and Paraguay merge-an area known as the Triple Border. In July 2000, more than 4.000.000 liters of crude oil leaked into the Iguazu River from a state-owned oil refinery in the municipality of Araucaria, near Curitiba.
