The rift is occupied in part by the largest freshwater lakes in Central America: Lago de Managua (56 kilometers long and 24 kilometers wide) and Lago de Nicaragua (about 160 kilometers long and 75 kilometers wide). These two lakes are joined by the Río Tipitapa, which flows south into Lago de Nicaragua. Lago de Nicaragua in turn drains into the Río San Juan (the boundary between Nicaragua and Costa Rica), which flows through the southern part of the rift lowlands to the Caribbean Sea.