The Guaraní knew it as y guasú — big water. In 1542, Álvar Núñez Cabeza de Vaca recorded the cataract for the Spanish crown and renamed it Salto de Santa María. The name did not hold. What survives is a basalt shelf on the Iguazú River: roughly 275 separate drops strung across nearly three kilometres of forested border between Argentina and Brazil. The route now covered by the iguazu falls tour boat ride train and safari truck circuit follows ground that naturalists first cleared by hand. Argentina created Parque Nacional Iguazú in 1934. Brazil answered with Parque Nacional do Iguaçu in 1939. UNESCO inscribed the Argentine park as World Heritage in 1984, the Brazilian park two years later. Together they shelter one of the largest surviving fragments of Atlantic Forest, a biome long reduced to scattered remnants. At the centre stands the Garganta del Diablo, a horseshoe some eighty metres deep that takes roughly half the river's volume and returns it as permanent mist. Access here has always been engineered. Narrow-gauge rails run from Estación Central through the interior to a catwalk laid across the upper river, and iguazu falls tour boat ride train and safari truck tours on both banks pair that line with open-sided vehicles and rigid-hull launches. Cataratas del Iguazú excursions from the Brazilian side descend instead through the forest toward Salto Tres Mosqueteros. Coatis work the walkways for scraps. Great dusky swifts nest behind the falling water, flying through the curtain at dusk to reach the rock. The result is one of South America's most photographed landmarks, best understood in parts. Distance belongs to the rails, force to the river, and context to the forest road — which is the argument the iguazu falls tour boat ride train and safari truck tour has always made. Isla San Martín sits mid-stream as evidence: an island reachable only by boat, holding a beach, a viewpoint, and a sightline into two countries at once.