Dan Snow climbs into the mountains on the trail of the lost city of the Inca, Machu Picchu, a magical metropolis perched high among the clouds. It was rediscovered, overgrown by jungle, more than 100 years ago. Now Dan explores its story and comes face to face with an Inca 'ice mummy' - a teenage girl frozen in time when she was sacrificed to the mountain gods 600 years ago.