The Devil's Throat (Garganta Do Diablo), Iguazu River, Brazil, Argentina Border

Geography
Iguazu Falls is 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 (1.7 mi) long edge divide the falls into about 275 separate waterfalls and cataracts, varying between 60 metres (200 ft) and 82 metres (269 ft) high. About 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-meter-high, 150-meter-wide, and 700-meter-long. The border between Brazil and Argentina runs through the Devil's Throat.
About 900 meters of the 2.7-kilometer 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 in 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 countries can be seen, a popular tourist attraction for visitors to the three cities.