Few landscapes in the American Southwest stir as much awe as Antelope Canyon. Hidden in the red sandstone near Page, Arizona, this narrow slot canyon has become one of the most photographed places in the world. Its smooth, sculpted walls seem to flow like water, glowing in shades of orange, gold, and purple. But before you can wander through its twisting passages, you face one question: Upper or Lower? Both parts of Antelope Canyon are inside the Lake Powell Navajo Tribal Park, and both can only be visited on a guided tour led by authorized Navajo guides. They’re close in…