Iguazu Falls was my favorite natural wonder of the trip. It has more annual flow than any other waterfall. It is comprised of 270 separate falls spanning 2/3 of a 2.7 km span. It is over twice the size of Niagara and is rivaled only by the Zambezi River's Victoria Falls in southern Africa. It is formed by the Iguazu River, a tributary of the Parana River (responsible for the Pantanal's flooding), which plunges over a plateau on Brazil's border with Argentina. Iguazu Falls is a UNESCO World Heritage Site.
I took an overnight bus from Campo Grande to Iguazu. I went straight to Brazil's Iguacu National Park (it's spelled with a "c" instead of a "z" in Portuguese) and took a helicopter ride over the falls. While Argentina's side of the falls has better views and more tourist activities, one can only book a helicopter ride on the Brazilian side.
Approaching the falls.
The thin structure spanning the water is a walkway from which tourists can peer into "La Garganta del Diablo", the largest of the falls. La Garganta plunges over 200 ft and sends mist 500 ft into the air, creating what are probably among the world's most beautiful rainbows.
La Garganta del Diablo.
Below: Imagining this photo taped to the bottom left corner of the pic above, one gets a sense of the position of the falls after the horseshoe in the Upper Iguazu.
I went to the town of Iguazu across the border in Argentina. It is much more quaint and pleasant than its sister city on the Brazilian side. The next day I visited Argentina's Iguazu National Park. Here are pics from the Lower Falls Trail.