We did part of our honeymoon there back in 1983. Iguazu is fantastic! We stayed on the Argentine side. In the area we also visited the Brazilian side, the Parana dam, Puerto Stroessner in Paraguay [different name now], some old Jesuit church ruins [did you see the DeNiro movie The Mission?] and some other things.

We also spent time in Buenos Aires, Montevideo, and Punta del Este. Punta del Este is definitely worth the visit.

Have a great visit!

Z