Iguacu Falls, I am told can be spelt in four different ways depending on which side of the border you're in, or if you use the local/native language. It has been on my list for a long time, but has until now eluded my travel plans. The falls are of course very impressive and a must on one hand, but the hords of tourists does take away quite a bit of the overall experience. There is a birds park called Parque Dos Aves on the Brazilian side and very close to the falls. This is worth a stop as well