The Inca fortress of Sacsayhuamán stands high above Cusco as a colossal mystery of construction. Its gargantuan stones, so precisely fitted, seem to defy rational explanation and have given rise to tales of demonic assistance. Deep in Rajasthan, India, the Chand Baori step well plunges 13 stories into the earth, its 3,500 perfectly arranged steps forming a hypnotic geometry so meticulous that locals whisper of unholy pacts. And in the heart of Paris, Notre-Dame Cathedral soars skyward, its Gothic spires and intricate ironwork pushing medieval engineering to such extremes that stories circulate of dark bargains. Did the creators of these structures truly strike a "deal with the devil," or do these wonders simply reflect the often-misunderstood genius of our ancestors?