There are but three great waterfalls in the world, and curiously they seem to all fall on borders: Niagara Falls, on the border between the United States and Canada; Victoria Falls, between Zimbabwe and Zambia; and Iguaçu Falls, between Brazil and Argentina.

I've seen them all. Iguaçu is without doubt the most beautiful of the three. Niagara is impressive, but marred by 2 centuries of industry and kitsch. Victoria Falls in Africa is higher, but also narrower, and the mist thrown up by all that water funneling into such a tiny gorge greatly obscures the view.

In Iguaçu, the water pours down over not one but some 275 different cataracts, spread over a precipice some 5km (3 miles) wide and 81m (266 ft.) high.

The fine mist tossed up by all that falling water precipitates down and creates a microclimate of lush rainforest, with tropical birds and an abundant population of glorious butterflies.

Iguaçu has been attracting visitors since the first European explorer stumbled across the area in the 1540s. In the 1930s more than 404,685 hectares (1 million acres) on the Brazilian side was made into a national park, and in 1985 the falls were designated a UNESCO World Heritage Site.

Iguaçu Falls never quite achieved the same iconic status as Niagara. The Iguaçu Falls did get one good breakout role, though, when they were cast almost as a supporting actor in the Robert DeNiro film, The Mission (worth renting for its story of the expulsion of the Jesuits, in addition to the great film footage of the falls).

Debate is endless as to whether the view from the Brazilian or Argentine side is better. You should really visit both sides to see for yourself.

Aside from the falls, there's not a lot to see in Iguaçu. Beyond the immediate zone of the falls, the national park is closed to visitors. The zodiac trips upstream toward the falls are highly recommended. There are also rubber raft trips through the rapids downstream, as well as an extraordinary 50m (164-ft.) rappel from the top of the gorge all the way down to the edge of the Iguaçu River.

The falls are remote enough that a 1-day trip is, well, insane. With a Brazilian air pass, Iguaçu makes a perfect 2-day stopover. Those with limited time, or money, should consider whether the falls -- glorious though they certainly are -- are worth the 1,000km (620-mile) trip from Rio or São Paulo.