The POWER of Water..Iguazu Falls are waterfalls of the Iguazu River on the border of the Brazilian state of Paraná and the Argentinian province of Misiones. The falls divide the river into the upper and lower Iguazu. The Iguazu River rises near the city of Curitiba. Ther river flows through Brazil for most of its course, although 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.