Antelope Canyon is the most-visited and most-photographed slot canyon in the American Southwest. It is located on Navajo land near Page, Arizona. Antelope Canyon formed over the course of millions of years by erosion of the Navajo Sandstone, primarily due to flash flooding and secondarily due to wind erosion. Rainwater (especially during monsoon season) runs into the wash that Antelope Canyon is part of, picking up speed and sand as it rushes through the narrow passageways. Over time the passageways are eroded away, making the corridors wider and smoothing hard edges in such a way as to form characteristic 'flowing' shapes in the rock. Lower Antelope Canyon, called Hasdeztwazi, or "spiral rock arches" by the Navajo, is located a few kilometers away from the upper Antelope Canyon and is a more difficult hike.