Waterworld

CORBIS

Iguazu Falls, as Eleanor Roosevelt famously observed, "make the Niagara look like a kitchen faucet." This may be an exaggeration but not by much—after all, the Iguazu Falls are four times wider than Ontario's most famous body of water. Located amid lush rainforest at the border of Brazil and Argentina, they present one of the best (and most deafening) opportunities you will ever have for an encounter with the unbridled power of nature.

The Brazilian side has the panoramas, while the Argentinean side offers proximity to the falls themselves. But viewing from both sides is necessary to complete...