The Misiones area had been a bone of contention for Argentina and Paraguay for decades. The War of the Triple Alliance, a union of Argentina, Brazil, and Uruguay, against Paraguay eventually clarified the border in 1870. While this war was unimaginably ruinous for Paraguay the other involved parties swung up to the wealthiest nations in South America. The picture was taken from the Argentine side in Puerto Iguazú. You see the border triangle at the confluence of the rivers Iguazú and Paraná. The lights on the left belong to Ciudad del Este in Paraguay, those on the right to the Brazilian city Foz do Iguaçu. Paraguay is separated from Brazil and Argentina by the Paraná River, whereas the Iguazú River forms the natural border between Argentina and Brazil.