The Rio Mapocho is a river that flows through Santiago, Chile's capital city, cutting through one of South America's most densely populated urban environments. Once considered a dead river plagued by wastewater, garbage, and foul odors, the Mapocho has undergone a remarkable ecological transformation over the past decade-plus. Thanks to sustained conservation efforts, wastewater outlets have been redirected to treatment plants, and the river now supports returning wildlife including fish, freshwater crabs, coipu (large South American rodents), and nesting birds. The river's characteristic brown, earthy color is not a sign of pollution — it results from sediment carried by the Canal San Carlos, which channels water from the Río Maipo into the Mapocho, giving it that distinctive tierra-toned appearance. The river originates in the Andes cordillera and descends through mountain terrain before passing through Santiago, carrying nutrients and sediments from the highlands that support a recovering aquatic food web.