The area that includes all of the tributaries for an individual stream or river is its drainage basin. For example, the drainage basin for the St. Lawrence River includes the area surrounding the Great Lakes. Rivers such as the Platte (which has its own drainage basin) flow into the Missouri, and the Missouri flows into the Mississippi. The combined area drained by the Platte, the Missouri, the Mississippi, and all other Mississippi River tributaries combined create the third largest drainage basin in the world. The Amazon has the largest drainage basin of any river, the Congo has the second largest.