The largest single cascade at Iguazu Falls is Garganta del Diablo, the Devil's Throat. The spray make for fantastic rainbows.
According to Wikipedia, the waterfall system consists of 275 falls along 2.7 kilometers. Some of the individual falls are up to 82 meters (269 ft), and the annual average discharge is 1746 m³/s, making it the 2nd largest remaining waterfall in the world (two larger ones have been inundated by reservoirs).
Photo 21 May, 2010 under relatively high-flow conditions.