Iguaçu National Park

Listen first. Before you see anything, you will hear it, a low and steady roar that seems to come from the ground itself. The air turns cool and damp against your skin. Fine mist drifts through the trees and settles on your arms, your glasses, your camera lens. The smell is wet earth, green leaves and river water. You are walking towards one of the largest waterfall systems on Earth, and the forest is announcing it long before the water appears.

Welcome to Iguaçu National Park, on the Brazilian side of the Iguaçu River. The name comes from Guaraní, the language of the Indigenous people of this region. It is usually translated as big water, which is an honest description. Across the river lies Argentina, with its own national park protecting the other bank. The two parks work as one landscape, split by a border that the river ignores completely.

Here is the first thing many visitors do not expect. Most of the waterfalls are actually on the Argentine side. So why come to Brazil? Because from this bank you look across at them. Argentina puts you close to the water, often right above it. Brazil gives you the panorama, the full curve of falling water in a single view. Many travellers visit both sides, and each one completes the picture the other one leaves open.

The falls stretch along a wide, crescent-shaped edge, close to three kilometres from end to end. The river here meets a step in the land, a series of hard volcanic rock layers formed by ancient lava flows. The water pours over these basalt ledges in dozens of separate cascades. The exact number changes with the season. In the rainy months, falls merge into walls of brown water. In drier periods, they separate into many white ribbons.

The Brazilian park was created in 1939, and UNESCO named it a World Heritage Site in 1986. A popular story links its protection to Alberto Santos-Dumont, the Brazilian aviation pioneer. According to the widely told account, he visited in the early twentieth century and was surprised that such a place was privately owned. He is said to have urged officials to bring the land into public hands. The story is repeated often here, so listen for it.

The main trail follows the edge of the canyon for roughly a kilometre. It is mostly paved, with steps and railings, and it drops gently towards the river as you go. Each bend opens a new viewpoint. At first you see the falls framed by branches. Then the trees fall away, and the whole amphitheatre of water fills your view. Take it slowly. The trail rewards people who stop often.

Now watch the ground near your feet. You will probably meet coatis, long-nosed relatives of the raccoon with ringed, upright tails. They move in groups, sniffing at bags and benches. They look friendly, but they are wild, and they can bite and scratch, especially when they smell food. Park signs ask visitors not to feed them. Keep snacks zipped away and simply enjoy watching them search the leaf litter.

The forest around you is part of the Atlantic Forest, a South American rainforest that once covered a huge stretch of the coast and interior. Much of it has been cleared over the centuries, which makes protected areas like this one especially important. The park shelters toucans, colourful butterflies, monkeys and even jaguars. The jaguars are rarely seen by visitors. But their presence tells scientists that the forest is still healthy enough to feed large predators.

Here is the second surprise. Look closely at the rock walls behind the falling water. You may see small dark birds diving straight into the spray and disappearing. These are swifts, and they nest on the wet cliffs behind the curtains of water. They fly through the falls to reach home. In the late afternoon, flocks of them circle above the river before they vanish into the mist.

The Guaraní people have their own story about how these falls were made. Legend has it that a serpent spirit called M'boi lived in the river. A young woman named Naipí was promised to him, but she escaped by canoe with a warrior named Tarobá. In anger, the serpent split the riverbed and created the falls. In the tale, Naipí became a rock below the water, and Tarobá became a palm tree on the edge above her.

At the end of the trail, a walkway reaches out over the river itself. Here you stand in front of the Devil's Throat, the largest and deepest part of the falls. It is a narrow, U-shaped chasm where a huge share of the river drops at once. The spray here is heavy. Within seconds you will be wet. Many people bring a light rain poncho, and many others simply decide to enjoy getting soaked.

When the sun is behind you, rainbows form in the mist. On a clear day they appear again and again along the canyon, sometimes as full arcs and sometimes as double bands. The light changes through the day, so the same view can look very different in the morning and afternoon. Near the walkway, an elevator carries visitors up to a higher viewing platform for one last look across the falls.

Before you leave, pause somewhere along the railing. Feel the vibration of the water through the metal under your hands. Notice how the roar never stops, never changes rhythm. This river has been falling over this rock for a very long time, and it will keep falling long after today. As you walk back through the trees, listen to the sound fading behind you, until only the forest and the birds remain.