Cataratas do Iguaçu are waterfalls of the Iguazu River on the border of the Argentine province of Misiones and the Brazilian state of Paraná. Together, they make up the largest waterfall system in the world. The falls divide the river into the upper and lower Iguazu. The Iguazu River rises near the heart of the city of Curitiba. For most of its course, the river flows through Brazil; however, most of the falls are on the Argentine side. Below its confluence with the San Antonio River, the Iguazu River forms the boundary between Argentina and Brazil.