The Paraguayan Chaco covers the entire western half of the country, separated from the more populated east by the Río Paraguay. It's a vast, flat expanse of dry thorn forest, savannah, and seasonally flooded grassland — one of the largest wilderness areas in South America and among the continent's most biodiverse ecosystems. Jaguars, giant anteaters, tapirs, maned wolves, peccaries, and hundreds of bird species inhabit its forests and wetlands.
Settlement is sparse. The eastern Chaco, closest to Asunción, contains Mennonite agricultural colonies that arrived from Russia and Canada in the 1920s–30s; their towns are orderly, German-speaking islands of dairy farms and co-operatives. Deeper into the Bajo Chaco and Alto Chaco, indigenous Ayoreo and other communities live in increasing isolation. The Trans-Chaco Highway cuts straight across to Bolivia, but much of the territory flanking it is accessible only by 4WD.
Filadelfia is the main Mennonite hub and the practical base for exploring the region. The dry season (May–September) is the only realistic time to travel here: roads turn to mud with heavy rain, and the heat in summer is extreme. The payoff for coming in the right season is extraordinary wildlife-watching, especially around water holes and river crossings.