A mile deep and two billion years of rock, carved by the Colorado River.
The South Rim viewpoints, such as Hopi Point and Mather Point, are open all year; the walls change colour with every hour of the day, and storms bring rainbows over the canyon.
Walk part of the Bright Angel Trail into the canyon, or raft the Colorado River for a week between its walls.
Photo: Tuxyso, CC BY-SA 3.0, Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Grand_Canyon_Hopi_Point_with_rainbow_2013.jpg)
