Across the globe and throughout history, ancient civilizations erected structures that continue to inspire awe and wonder. But how did they do it? And what secrets lie hidden within the walls of these incredible monuments? Archaeological finds and new technologies reveal clues to long-enduring mysteries. How did the Celts build Newgrange to last, even through cataclysmic flooding? And how do Mayan pyramids like those found at El Castillo hold clues to an ancient civilization's advanced understanding of the cosmos? As ancient edifices reveal design almost beyond comprehension, does captivating geometry like that found at the Chand Baori stepwell hint at otherworldly interference? From the iconic arches of Rome's Colosseum, to a fortress perched atop a remote volcano in Sri Lanka; from the colossal stone sculptures that dot an island in the Pacific, to an iconic wall that spans a whole continent, and the glimmering pools of Angkor Wat, what ancient secrets can be revealed about the ancient structures that have shaped our world?