Madeira River

Madeira River, largest tributary of the Amazon River. Flowing northeastward, this important South American waterway runs along the Brazil-Bolivia border and continues for approximately 2,000 miles (3,200 km)—some of which are still uncharted or explored. The river is navigable by boat for the first 700 miles (1,126 km), then a railroad follows the riverbank for more than 200 miles (320 km) of rapids. The river opens into the Amazon east of the city of Manaus, Brazil.