These cities are capitals of the provinces of Chaco and Formosa, which constitute a region known as Gran Chaco that occupies the vast lowlands of center-northern Argentina, as well as parts of Bolivia and Paraguay. The climate here becomes drier from east to west, splitting the region in two merging parts. The Dry Chaco in the west is likely to appeal only to the most adventurous spirits. Its wildlife is very diverse, specially with regards to snakes, but even reptile-lovers may find it hard to get around in the region, for the country is covered with dense thorn thickets, scarce roads and no facilities for visitors at all.

The area of the Argentine littoral called Wet Chaco stretches towards the northwest in Formosa and Chaco provinces, both covered with subtropical forests. Although it has undergone some major clearance for agriculture, it still contains beautiful tracts of woodlands interspersed with marshes. Its marshes and rivers are habitat for diverse fauna species, which led to the creation of the Pilcomayo River National Park, on the right margin of the mentioned river, in the Province of Formosa. Created in 1951, this park protects an area where marshes, Palma Blanca and Caranday savannah prevail. There are woods in the highlands, and dense jungle on the riverbanks. One of the gateways to this area is the route starting in the city of Clorinda, some 40 km (25 miles) from Asunción in Paraguay and 15 km (9 miles) from the park, continuing afterwards along its southern boundary. Another access is Formosa airport, situated 112 km (70 miles) away.

In the province of Chaco, some 100 km (63 miles) northwestward from Resistencia, stands the Chaco National Park with examples of all characteristic ecosystems of the Eastern Chaco District. The southern and center areas are covered by forests where quebracho colorado trees stand out; the western area represents the typical ecosystem of savannah with Caranday palm-trees; finally, in the southeastern area, the Panza de Cabra Lagoon exhibits an abundant aquatic vegetation. The local fauna consists of a wide variety of mammals, but the main attraction is its wide assortment of birds. It is better to avoid the wet season in summer (from December to March) for heat is intense and roads become impassable.

In the provinces of Chaco and Santiago del Estero there is a large area called Campo del Cielo (Sky Land), where 13 iron-nickel meteorites have been found. The so-called "Chaco" meteorite weighs 33,400 kg and stands out for being the biggest to ever fall in our country and the third one in the world.