Thousands of years of wind, water, and glacial erosion have carved out these eerie badlands 400 feet (122 meters) below prairie level in Alberta, Canada’s Horsethief Canyon. Legend has it that during the region’s ranching heyday, horses would sometimes disappear into the canyons and emerge later marked with different brands, hence the canyon’s curious name.

(Photograph shot on assignment for, but not published in, the National Geographic book Trans-Canada Highway, 1986)