One of the continent’s most spectacular sights, despite recent 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 rainforests 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 surprisingly vigorous cultural and artistic life, as a base for visiting the Chaco and Río Pilcomayo national parks. This, though, is best in the cool winter.

In southernmost Mesopotamia, destinations like Gualeguaychú (for Carnaval), Parque Nacional El Palmar, and Rosario are close enough for weekend excursions from Buenos Aires.