The Garganta del Diablo — Devil's Throat — is the centrepiece of the Argentine side and the most spectacular single viewpoint at Iguazú. It is a U-shaped chasm at the upper end of the falls where the Iguazú River drops 82 metres in a continuous wall of white water, generating a permanent cloud of mist visible from kilometres away.
The park's internal train takes you partway, and a long boardwalk crosses the river to bring you out at the lip of the falls themselves. The viewing platform sits directly above the cascade. The noise is extraordinary — a sustained roar that makes conversation impossible — and the spray soaks you within minutes. On sunny days, rainbows form continuously in the mist.
Come early in the morning for the best light and before the day-trip crowds arrive from both sides of the border.