Argentina
These falls are simply magnificent. Bigger and better than either the Virginia or Niagara falls apparently. They can be easily visited from either the Brazilian or Argentinian side by public transport. The Brazilian side was my favourite as you get views of the whole of the falls.
The Argentinian side gives you a more up-close-and-personal view but not one of the grandeur of them. If you have time go to both sides.
Search Been there