I've been to Niagara Falls more times than I can count, and it is ALWAYS simply incredible. I've stood by the falls for hours, until soaked by the spray. I've also been there when the smaller section (The American falls) was frozen.
22 Magical Places You MUST Visit at Least Once in a Lifetime
Iguazu Falls, Brazil are waterfalls of the Iguazu River on the border of the Brazilian state of Paraná and the Argentine province of Misiones. The falls divide the river into the upper and lower Iguazu. One of the 7 natural wonders of the world