On road maps of northern Argentina there is a straight line between the Paraná River at Resistencia, the capital of Chaco province, across Chaco and the northeastern corner of Santiago del Estero, back into Chaco for 16 kilometers, then on to Macapillo in Salta province — 552 kilometers. You would be forgiven for thinking that a straight line means a straight road.

Well, Route 16 is, almost. In fact, there are 38 curves or, more precisely, nineteen pairs of curves. Usually the first curve is to the left, then to the right. Why? Because the highway can’t run straight through a gigantic communications tower. Why wasn’t the highway located south or north of these towers? Don’t ask. This is Argentina.

This slightly curled ribbon of road is the link between two dramatically different parts of the country. On the eastern end lies Corrientes, home to vast estancias (ranches/stations) and wetlands. Attached to Corrientes on its northeast corner is the finger-shaped province of Misiones: undulating, forested hills, many with tea and mate plantations, ending at the Brazilian border and Iguazu Falls.

West of Macapillo the hills begin again, at first gently then more steeply as the road climbs toward the Andes.

Driving southwest from Iguazu on Route 12 is like being on an endless, very long rollercoaster between green walls. The small city of Puerto Rico demanded a stop just because of its name. It was not named for the Caribbean island but because it became an important port on the Paraná in the early 20th century. The Paraná is big-ship navigable almost all the way to Iguazu. The German settlers who founded the town in the late 19th century exported lumber and mate (pronounced “MAH-tay”-the famous Argentine herbal tea) from here.

Further south is San Ignacio, the most famous of the many Jesuit missions that were established in the 16th century, and beyond that Santa Ana, less well known and preserved, but larger than San Ignacio.

Entrance to the church at San Ignacio. Note the different styles of columns on each side of the doorway. Outside are Roman columns; inside are Guarani designs. The Guarani were a nomadic people who ranged across a wide swath of what is today Brazil, Paraguay, Bolivia, and Argentina. After the Jesuits arrived in the 17th century, they persuaded the Guarani to settle, become monogamous, and Christian. The result was the first literate society in Latin America. The missions collapsed when the Jesuits were expelled from Latin America in 1767.

Turning more westerly, the road begins to flatten out, passes Posadas, capital of Misiones province, and follows the river for 390 kilometers to Corrientes, that province’s capital directly across the river from Resistencia.

A Paraguayan boatman paddles home across the Paraná River from Puerto Rico.

Along the way estancias extend as far as the eye can see; the Esteros del Iberá wetlands lap against a low berm for several kilometers, and a large sign signals the entrance to one of Argentina’s largest hydroelectric projects, Yacyreta-Apipé dam. There are four daily tours of the dam but, arriving too late, we had to content ourselves with a tour of the splendidly done museum. It has two parts: a detailed explanation of the dam and how it operates, complete with mock-ups of the turbines; and, a collection of pre-Columbian artifacts recovered during the excavation.