The Río Antiguo Cauce del Pilcomayo — the ancient former channel of the Pilcomayo River — winds through the subtropical lowlands of the Argentine Chaco, a region defined by seasonal flooding, dense riparian vegetation, and remarkable biodiversity. This water body exists within and adjacent to the Río Pilcomayo National Park in Formosa Province, where the old channel and its associated wetlands form a mosaic of aquatic habitats ranging from slow-moving backwaters to seasonally flooded floodplains. The surrounding landscape is dominated by riparian forest featuring figs, sweetwood trees, and a dense tangle of lianas, vines, and epiphytes along the banks, while the broader wetland zones are carpeted with floating aquatic vegetation including water hyacinths, Nymphoides, and Ludwigia species. This is a remote, wild, and ecologically rich fishing destination that rewards anglers who appreciate the raw character of South American tropical and subtropical fisheries.