Entry & Exit Formalities
Many nationalities can enter Argentina without a visa, but double-check before you arrive or at the Argentine Consulate. Argentina had suspended the reciprocity fee that previously saddled Americans, Australians and Canadians with a hefty bill to cross into the country at time of writing, but it's always best to check ahead.
For Paraguay, Americans ($160), Australians ($135) and Canadians ($150) need a visa – though not unless you go beyond Ciudad del Este. Get this in advance at home or from the Paraguayan Consulate in Foz.