We visited Iguazu Falls last year and I have to say it was one of the most impressive natural sights I have ever seen: far, far more spectacular than Niagara Falls. Most people seemed to prefer the Brazil side (great photos here: www.realworldholidays.co.uk/multi/guide/iguazufalls.aspx) but for me the Argentina side where you get right up close to the Falls was the real highlight. Have to say, unlike with most waterfalls and such like, I would happily re-visit it.