The Grand Canyon gives no warning. At Mather Point, on the South Rim in northern Arizona, you come out of low piñon pine and juniper and the ground simply ends. Sixteen hundred metres of open air drop away, flat-topped buttes go back rank after rank into the haze, and the far rim is a pale line as much as twenty-nine kilometres off. From the same railing you can read the wall downwards. Every flat band is a landscape that no longer exists, a shallow sea or a desert stacked on the one before, down to the dark rock at the river, among the oldest exposed on the continent. Near the bottom the order breaks: sandstone 525 million years old sits straight on rock 1.7 billion years old, and at a few places by the water you can lay a hand across the join and touch both sides of a billion missing years. West along Hermit Road the canyon widens and every overlook reframes it. On late-summer afternoons the monsoon builds, rain drags in curtains across the gorge, and a rainbow can arch clear over the buttes.
Under the rim it stops being a view. The Bright Angel Trail switchbacks down an old mule path, and with every bend the walls close over you and the air turns warmer and drier. Going down is deceptively easy. The climb back through the afternoon heat is the work, and most walkers turn at a resthouse and leave the river for another trip. Deeper still the Colorado is run for days at a time, the rim sixteen hundred metres above the raft and the nights spent on sandbars where no engine can be heard at all. On a moonless night the darkness here is the kind that has almost gone from the world. And somebody lives down there. Off a side canyon to the west, on Havasupai land beside its blue-green waterfalls, the village of Supai has no road to it: the people, the supplies and the mail all cover the last thirteen kilometres by mule.