The Colorado river and its tributaries took a hundred million years or two to carve the Glen Canyon out of the pink and scarlet sandstone which marks out the American southwest. Its myriad gorges, sheer cliffs and towering spires remained a largely hidden secret.

Prehistoric peoples farmed part of the canyon and Navajo Indian communities built camps close to the river, but few modern Americans ventured there besides explorers until the canyon disappeared under a man-made wonder, the vast Lake Powell, with the construction of Glen Canyon dam half a century ago. Almost immediately, environmentalists and archaeologists mourned the loss. A final burst of exploration had turned up thousands of ancient ruins and drawn a belated focus on the canyon’s stunning natural architecture. FULL REPORT