6. Slot Canyons, Arizona and Utah Slot canyons are narrow and incredibly deep gorges (they can be less than three feet across yet well over 100 feet deep!) formed by water rushing through sandstone and limestone. Located in Arizona and Utah (among other places like Spain, Australia and France) their unique shapes have evolved through years of wear from water rushing through during the typical flash floods. Antelope Canyon, located on Navajo Nation land, just outside Glen Canyon National Recreation Area is the most visited slot canyon in the Southwest. Grand Wash is another deep but easily accessed canyons along the scenic drive at the center of Capitol Reef National Park.