The Cedar Mesa area of Utah is divided by many canyons that were the home to ancient cliff-dwellers. The sheltered nooks and alcoves in which they built their homes and granaries protected them from the elements and are one reason that the ruins remain relatively intact to this day.
Many of the rocks in the foreground were once part of the "roof" of this alcove, and when they fell, they exposed a layer of stone that almost glows when photographed.