The name "Iguazú" comes from the Guarani or Tupi words "y" [ɨ], meaning "water", and "ûasú "[waˈsu], meaning "big". Legend has it that a deity planned to marry a beautiful woman named Naipí, who fled with her mortal lover Tarobá in a canoe. In a rage, the deity sliced the river, creating the waterfalls and condemning the lovers to an eternal fall. The first European to record the existence of the falls was the Spanish conquistador Álvar Núñez Cabeza de Vaca in 1541.
The Iguazu Falls are located where the Iguazu River tumbles over the edge of the Paraná Plateau, 23 kilometres (14 mi) upriver from the Iguazu's confluence with the Paraná River. Numerous islands along the 2.7-kilometre-long (1.7 mi) edge divide the falls into many separate waterfalls and cataracts, varying between 60 to 82 metres (197 to 269 ft) high. The number of these smaller waterfalls fluctuates from 150 to 300, depending on the water level. Approximately half of the river's flow falls into a long and narrow chasm called the Devil's Throat (Garganta del Diablo in Spanish or Garganta do Diabo in Portuguese). The Devil's Throat is U-shaped, 82 by 150 by 700 metres (269 ft × 492 ft × 2,297 ft). Placenames have been given also to many other smaller falls, such as San Martín Falls, Bossetti Falls, and many others.
About 900 metres (2,950 ft) of the 2.7-kilometre (1.7 mi) length does not have water flowing over it. The edge of the basalt cap recedes by 3 mm (0.1 in) per year. The water of the lower Iguazu collects in a canyon that drains into the Paraná River, a short distance downstream from the Itaipu Dam. The junction of the water flows marks the border between Brazil, Argentina, and Paraguay. There are points in the cities of Foz do Iguaçu, Brazil, Puerto Iguazú, Argentina, and Ciudad del Este, Paraguay, which have access to the Iguazu River, where the borders of all three nations may be seen, a popular tourist attraction for visitors to the three cities.
The Iguazu Falls are arranged in a way that resembles a reversed letter "J". The border between Brazil and Argentina runs through the Devil's Throat. On the right bank is the Brazilian territory, which has just over 20% of the jumps of these falls, and the left side jumps are Argentine, which make up almost 80% of the falls.
There are two international airports close to Iguazú Falls: the Argentine Cataratas del Iguazú International Airport (IGR) and the Brazilian Foz do Iguaçu International Airport (IGU). Argentina's airport is 25 kilometres (16 mi) from the city of Iguazu, but is closer to the falls hotels than its Brazilian counterpart. There are bus and taxi services from and to the Airport-Falls. Brazil's airport is between Foz do Iguaçu, Brazil, and the falls. Aerolíneas Argentinas and LATAM Argentina have direct flights from Buenos Aires to Iguazu International Airport Krause. Azul, GOL, and LATAM Brasil offer services from main Brazilian cities to Foz do Iguaçu.
The falls may be reached from two main towns, with one on either side of the falls: Puerto Iguazú in Argentina and Foz do Iguaçu in Brazil, as well as from Ciudad del Este, Paraguay, on the other side of the Paraná river from Foz do Iguaçu. The falls are shared by the Iguazú National Park (Argentina) and Iguaçu National Park (Brazil). The two parks were designated UNESCO World Heritage Sites in 1984 and 1987, respectively.
The first proposal for a Brazilian national park aimed at providing a pristine environment to "future generations", just as "it had been created by God" and endowed with "all possible preservation, from the beautiful to the sublime, from the picturesque to the awesome" and "an unmatched flora" located in the "magnificent Iguaçú waterfalls". These were the words used by André Rebouças, an engineer, in his book "Provinces of Paraná, Railways to Mato Grosso and Bolivia", which started up the campaign aimed at preserving the Iguaçu Falls in 1876. At this time, Yellowstone National Park in the U.S., the first national park in the world, was four years old.
On the Brazilian side, there is a walkway along the canyon with an extension to the lower base of Devil's Throat. Helicopter rides offering aerial views of the falls have been available from Brazil, however, Argentina has prohibited such helicopter tours because of the adverse environmental impact on the flora and fauna of the falls. From Foz do Iguaçu airport, the park may be reached by taking a taxi or bus to the entrance of the park. There is an entrance fee to the park on both sides. Once inside, free and frequent buses are provided to various points within the park. The town of Foz do Iguaçu is approximately 20 kilometres (12 mi) away, and the airport is between the park and the town. The Argentine access, across the forest, is by a Rainforest Ecological Train very similar to the one in Disney's Animal Kingdom. The train brings visitors to the entrance of Devil's Throat, as well as the upper and lower trails. The Paseo Garganta del Diablo is a 1-kilometre-long (0.6 mi) trail that brings visitors directly over the falls of Devil's Throat, the highest and deepest of the falls. Other walkways allow access to the elongated stretch of falls across the forest on the Argentine side and to the boats that connect to San Martin Island. Also on the Argentine side, there are inflatable boat services that take visitors very close to the falls.
The Brazilian transportation system aims at allowing the increase in the number of visitors, while reducing the adverse environmental impact, through an increase in the average number of passengers per vehicle inside the park. The new transportation system has 72-passenger capacity, panoramic-view, double-deck buses. The upper deck is open, which enables visitors a broad view of the flora and fauna during the trip to the falls. The bus combustion systems are in compliance with the CONAMA (phase IV) and EURO (phase II) emissions and noise requirements. The reduction in the number of vehicles, of noise levels, and speed, is enabling tourists to observe increasing numbers of wild animals along the route. Each bus has an exclusive paint scheme, representing some of the most common wild animals found in the Iguaçú National Park, including the spotted jaguars, butterflies, raccoons, prego monkeys, coral snakes, toucans, parrots, and yellow breasted caimans.
Upon seeing Iguazu, the United States First Lady Eleanor Roosevelt reportedly exclaimed "Poor Niagara!" (which, at 50 m or 165 feet, are a third shorter). Often Iguazu also is compared with Victoria Falls in Southern Africa, which separates Zambia and Zimbabwe. Iguazu is wider, but because it is split into approximately 275 discrete falls and large islands, Victoria has the largest curtain of water in the world, at more than 1,600 m (5,249 ft) wide and over 100 m (328 ft) in height (in low flow Victoria is split into five by islands; in high flow it may be uninterrupted). The only wider falls are extremely large rapid-like falls, such as the Boyoma Falls (Stanley Falls).
With the flooding of the Guaíra Falls in 1982, Iguazu currently has the sixth-greatest average annual flow of any waterfall in the world, following number five Niagara, with an average rate of 1,746 m3/s (61,660 cu ft/s). Its maximum recorded flow was 45,700 m3/s (1,614,000 cu ft/s) in 9 June 2014. By comparison, the average flow of Niagara Falls is 2,400 m3/s (85,000 cu ft/s), with a maximum recorded flow of 8,300 m3/s (293,000 cu ft/s). The average flow at Victoria Falls is 1,088 m3/s (38,420 cu ft/s), with a maximum recorded flow of 7,100 m3/s (250,000 cu ft/s).
The Iguazu Falls experience a humid subtropical climate (Cfa, according to the Köppen climate classification) with abundant precipitation and high temperatures year-round. During the summer of 2006, a severe drought caused the Iguazu River to become diminished, reducing the amount of water flowing over the falls to 300 cubic metres per second (11,000 cu ft/s) until early December. This was unusual, as dry periods normally last only a few weeks.