 Experts are working to make sense of a three-sided metal monolith that was discovered in the Nevada desert outside Las Vegas this month. Some of the mysterious objects have been spotted across the world over the past four years, but the question of who made many of them remains a mystery. NPR's Joe Hernandez has more. In late 2020, Utah officials discovered a three-sided shiny metallic column in a remote area of red rocks. They didn't know who made it or how it got there.