Northeast of modern-day Mexico City stand the remnants of one of the world's largest preindustrial cities, Teotihuacan. Monumental in scale, Teotihuacan is organized along a three-mile-long thoroughfare, the Avenue of the Dead, that leads up to the massive Pyramid of the Moon. Lining the avenue are numerous plazas and temples, which indicate that the city once housed a large population that engaged in complex rituals and ceremonies. Although scholars...