This picture was taken during a 3 weeks trip to Argentina. The Iguazu Falls masterfully mark this border between Brazil and Argentina. In my opinion, they are the most beautiful and impressive in the world. You can observe a rich fauna, especially the endemic great dusky swifts ( Cypseloides senex ). These small birds, emblematic of the falls, nest on the cliffs, often behind the curtains of water, which allows them to be protected from predators, as well as their offspring. And it is disconcerting to see how easily they cross these cataracts! Their brio command admiration !