S1, E5: To celebrate his god-like status as 'Sun of the Sun God', the creator of the Inca Empire, Pachacuti the Conqueror (his name means 'World-Shaker'), orders the building of an 'impossible' city in the sky - a sacred residence where he will commune with his fellow gods - the sun, moon, thunder, and mountains. The site, high in the Andes, perched almost two-and-a-half kilometers above sea level, on a narrow ridge of volcanic granite, faces the Emperor's engineers with an almost impossible task. How to make sure the city, where they will erect spectacular temples, altars, residences, and fountains - all built on shifting fractured rock - will resist the torrential rains, landslides, and earth tremors of the region. Brilliantly conceived, perfectly executed, using techniques that even surpass those of today - and mystify architects, engineers, and archeologists - the Inca create their masterpiece: Machu Picchu. When Spanish Conquistadores and European smallpox destroy the Inca Empire, Machu Picchu is abandoned, lost, and forgotten - living on only in legend. Rediscovered, covered in jungle, only 100 years ago, Machu Picchu remains today, just as the Emperor Pachacuti intended, one the most spectacular - awe-inspiring and mysterious - monuments in the world.