This photograph shows a section of the Negro River in Jau National Park, Amazonas state. Fed by multiple waterways, the Negro River is the Amazon's largest tributary. The mosaic of partially-submerged islands visible in the channel of this enhanced satellite image disappears when rainy season downpours raise the water level. Jau National Park is South America's largest forest reserve, covering 23,000 sq km (8,900 sq mi); it is listed as a UNESCO World Heritage Site. Image courtesy of USGS.