The Iguassu Waterfalls are situated inside the Iguassu National Park. They were formed 150 million years ago and consist of 275 single falls, which merge into one large waterfront during times of flooding. There are 19 large falls, of which only 3 are to be found on the Brazilian side (Floriano, Deodoro and Benjamin Constant).

The word "Iguassu" means "Great Water" in the language of the Tupy Guarani Indians. The river originates in the Serra do Mar and runs for 1320 km through the state of Paraná before it flows into the river Paraná at Foz do Iguassu.

Before reaching the falls the river flows round a wide bend and down some rapids and then falls laterally to the bottom of a huge erosion fissure, forming the "Garganta do Diabo".
Above the falls the river measures 1200m in width, it narrows down to 65 – 100m in the tectonic fissure which forms the bottom of the gorge. The width of the falls is 800m on the Brazilian side and 1900m on the Argentinean side, so all in all the semicircular waterfront of the falls measures 2700m. Including a rapid above the falls the height is 72m. Depending on the changing water level during the seasons the number of the falls varies between 150 and 275, their height varies between 40 and 90m. Depending on the rain fall the water flow varies between 1500m³/sec and 6500m³/sec with an average flow of 1500m³/sec.