Slot, or slit, canyons are rare formations, the result of the combined forces of wind and water on sandstone. The narrow crevice sliced through a mesa by rushing water evolves from a hairline crack into a series of convoluted hollows, in some instances stacked many stories high. Little light enters, but its quality, as ﬁltered, refracted, reﬂected, and observed from below, illuminates incandescent striations of the sandstone as it has been etched over centuries by the ﬂow of subterranean rivers. In 1931, a twelve-year-old girl was herding sheep in what is now the Navajo Indian Reservation in the Four Corners region when she discovered the country’s best-known slot canyon. It’s most often called Antelope Canyon, but is also referred to as Corkscrew, Upper Antelope, Wind Cave, or the Crack. A slot canyon that looks as if it has been cut out of the sandstone with a saw is called a saw-cut canyon. Most U.S. examples of this feature are found in Arizona’s Glen Canyon, and include Labyrinth Canyon, which is about three miles of a twisting, turning passage that’s no more than two or three feet wide at the bottom and hundreds of feet high.