Who made Stonehenge and how? What lies beneath the lost city of Petra? What brought an end to Mayan civilization? How did Utah's celebrated arches form? This revealing special issue from National Geographic demystifies science, physics, and engineering and examines the cultural forces that created the most mysterious natural and manmade wonders of the world. Filled with vivid illustrations and intriguing anecdotes, 100 Greatest Mysteries Revealed peels back the layers of time to illuminate some of the most coveted secrets of all time.