Antelope Canyon is the most-visited and most-photographed slot canyon in the American Southwest. It was formed by erosion of Navajo Sandstone, primarily due to flash flooding. Rainwater, especially during monsoon season, runs into the extensive basin above the slot canyon sections, picking up speed and sand as it rushes into the narrow passageways. Over time the passageways are eroded away, making the corridors deeper and smoothing hard edges in such a way as to form characteristic 'flowing' shapes in the rock.

Unlike the winter trip, this time around, I visited the "Upper Antelope Canyon". It is the one most frequently visited by tourists, due to two considerations. First, its entrance and entire length are at ground level, requiring no climbing. Second, beams (shafts of direct sunlight radiating down from openings in the top of the canyon) are much more common in Upper than in Lower.