Straddling the borders of Brazil and the Argentina and the largest waterfall system in the world, the Iguaza Falls are a treat for both the eyes and ears. I don’t think I quite appreciated their sheer size and if you are able, try and experience the falls from both sides – the Brazilian side gives you the ‘big picture’ while you can get very close on the Argentinian side. I would budget at least a day for each.
If budget permits, you can catch a boat to under the falls – it’s an incredible experience and one best done just before mid-day so you can dry off in the heat of the day. It’s an expensive but unforgettable experience.