In this first part of a two-episode series, we're headed to the Valley of Mexico to explore one of the world's greatest - and most underrated - cities and the stories it tells about the connection between art and science. In this episode, we begin at the beginning to see how the unique natural history of the valley has shaped human culture in the cities that have grown up here, from ancient Cuicuilco, to Tenochtitlan on the eve of the Spanish Conquest, the modern-day Mexico City.