Grand Canyon National Park

Stand still at the rim for a moment. Feel the cool, thin air on your face. On the South Rim you are about two thousand metres above the sea, and the wind carries the sharp, clean smell of ponderosa pine. Then look out. The ground simply stops. Below you, layer after layer of red, cream and grey rock falls away into blue haze. Sound behaves strangely here. A raven calls, and the call seems to come from nowhere.

This is Grand Canyon National Park, in northern Arizona's Coconino County. The numbers are hard to hold in your head. The canyon runs for roughly 446 kilometres along the Colorado River. In places it is close to thirty kilometres wide. And it is about 1,800 metres deep, a little more than a mile. Your eyes will try to make sense of that depth. Most people find they cannot. The far rim looks close enough to call across to, yet it is many kilometres away.

The river did most of this work. You may not even see it from where you stand. From many viewpoints the Colorado is a thin brown or green thread, or hidden completely behind the inner cliffs. Over millions of years, the river cut down while the land around it slowly rose. Rain, frost and flash floods widened the gap. Rock fell from the walls, and the river carried it away. That process has not stopped. It is happening right now, just very slowly.

Now look at the layers in the canyon walls. Each band is a different chapter of the Earth's past. The pale rock near the rim is called Kaibab Limestone. It formed in a warm, shallow sea, roughly 270 million years ago. If you look closely at rocks along the rim trails, you may spot fossil shells and sponges inside them. So the stone under your feet, two kilometres above sea level, was once the floor of an ocean.

Here is something many visitors miss. Deep in the inner gorge, near the river, the rock turns dark and twisted. Geologists call it the Vishnu Schist. It is close to two billion years old, among the oldest rock exposed anywhere in this part of the continent. And directly on top of it, in many places, sits a much younger sandstone. Between the two, more than a billion years of history is simply missing. Geologists call this gap the Great Unconformity. Rock from that long stretch of time was worn away before the sandstone settled on top.

People were here long before any of that was understood. Ancestral Puebloan peoples built homes and granaries in and around the canyon. Today several Native nations keep deep ties to this landscape, including the Havasupai, Hualapai, Navajo, Hopi, Paiute and Zuni peoples. The Havasupai still live inside the canyon system, in a village that can only be reached on foot, by mule or by helicopter. For these communities, the canyon is not scenery. It is homeland, and many places here are sacred.

The first Europeans to see the canyon were Spanish soldiers, in the sixteenth century. They could not find a way down to the river and turned back. Much later, in 1869, a one-armed Civil War veteran named John Wesley Powell led a small expedition by boat down the Colorado. They were mapping a blank space on American charts. Food ran low, boats were lost, and some men left the trip. Powell's reports helped bring the canyon to national attention.

Protection came step by step. President Theodore Roosevelt visited in 1903 and urged Americans to leave the canyon as it was. In 1908 he made it a national monument. Then, in 1919, Congress made it a national park. Decades later, in 1979, the canyon was added to the UNESCO World Heritage List — a register of places considered important for all of humanity. Today it receives millions of visitors every year.

Look around the historic buildings of Grand Canyon Village, and you will see the work of an architect named Mary Colter. In the early twentieth century, at a time when few women led building projects, she designed several structures here. Hopi House, Lookout Studio and Hermits Rest are among them. Further east stands her Desert View Watchtower. Colter used local stone and rough timber. She wanted her buildings to look as if they grew out of the rim itself.

The canyon also has two very different rims. The South Rim, where most people arrive, stays open all year. The North Rim sits higher, at roughly 2,500 metres, so it is cooler and gets heavy snow. It is open only part of the year. Here is a surprise: the two rims are only about sixteen kilometres apart as the raven flies. But the drive between them takes more than four hours. There is no bridge across the canyon at the rim.

Watch the sky as well as the rock. Ravens ride the rising air along the cliffs. If you are lucky, you might see something much larger — a California condor, with wings close to three metres across. These birds almost disappeared in the twentieth century. They were released back into northern Arizona in the 1990s, and some now soar over the canyon. Many carry numbered tags on their wings, which helps biologists track each bird.

The heat inside the canyon is a different world from the rim. As you go down, the air gets warmer and drier. In summer, the bottom can be dangerously hot, even when the rim feels pleasant. Park rangers repeat one simple warning: going down is optional, but coming back up is mandatory. Every year, hikers underestimate the climb out. If you walk below the rim, carry plenty of water and salty food, and turn around early.

The light changes everything here. At midday, the colours look flat and pale. Shadows are short, and the layers blend together. But in the early morning and late afternoon, low sunlight cuts across the walls. Ridges and side canyons stand out in sharp relief. Reds become deeper, and the distant buttes turn orange, then purple. Many people stay at one viewpoint for an hour, simply watching the colours shift.

Before you walk away, take one last look. Find the darkest, deepest line of rock you can see, far below. That stone was already ancient when the oldest dinosaurs lived. Then listen. The wind, a distant voice, the scrape of your own shoes on the limestone rim — the rock under those shoes was once the floor of a sea. Take your time on the path back. The canyon will still be here, changing slowly, long after today.