Iguazu Falls is a complex of about 275 seperate waterfalls on the Iguazu River on the Argentina-Brazil border. Both Argentina and Brazil have established National Parks on their respective portions of the falls and they have done an excellent job of preserving the area, particularily when you consider the huge number of visitors it has each year.
Compromises have been made to accomadate the tourist traffic. A small train takes people from the visitors center on the Argentine side to the portion known as the Devil's Throat, as well as a stop to the other two main falls trails. This eliminates the need for buses in this area.
The Falls themselves can be reached by a system of catwalks and lookouts which provide excellent views to various portions of the falls while remaining fairly unobtrusive, They are all accesible to the disabled.
One thing that is obtrusive is the helicopter rides leaving every seven minutes from the Brazil side. They are very noisy, pollutive, and disruptive of the wildlife. Only one one helicopter is allowed in the air at once, an improvemt from past years when as many as eight would be airborne, but they are still a very jarring element.
A slideshow of the Falls is here
Over 400 species of birds have been found in the area. The area is most famous for the Great Dusky Swift, hundreds of which can be seen flying through the mist of the falls, and whch nest on the rocks behind the falls.The Toucan family has a few representatives to be found here and the large Toco Toucan is commonly seen.
The summary of Argentine bird images is here
One
of the most amazing things about the area is the incredible profusion of butterflies.
In the early morning, you can find them setting on rails and plants, an abundance
of different types. As the sun begins to dry their wings, they start to fly
about, at times you can see many dozens in one view. Many types come together
in assemblies, literally hundred of individuals in close proximity.