One of the continent’s most spectacular sights, despite some negative developments, Iguazú  alone demands at least three days from any visitor, preferably during the full moon; if the trip includes the Brazilian side, an additional day or two is desirable, and exploring the area’s more remote rain forests could add even more. For the mission at San Ignacio , figure at least another day.
Add no less than three days to tour the Esteros del Iberá  at Colonia Pellegrini , and figure a day to get there and a day to get back via the city of Mercedes  (there’s quicker access from the city of Posadas  in dry weather). Iberá, though, is worth a trip in its own right—even at the cost of bypassing Iguazú . Both Iguazú and Iberá are worthwhile at any season—even during the withering summer heat and humidity.
Travelers wishing to explore areas with few foreigners can use the Chaco provincial capital of Resistencia , with its vigorous cultural and artistic life, as a base for visiting the Chaco  and Río Pilcomayo National Parks . This is best in the cool winter, however.