Connecting these massive pyramids is the spine of the city: the Avenue of the Dead, or Calzada de los Muertos. This grand boulevard stretches for nearly 2 kilometers, or about one and a quarter miles. Despite its macabre name given by the Aztecs, archaeologists believe this was a vibrant urban center lined with administrative buildings, temples, and luxury residential compounds for the city's elite. As you walk this path, imagine it at its peak in 400 AD, when it was the main artery for a population of up to 100,000, or even 200,000 residents. A practical tip for your visit: the walk is entirely open to the elements with very little shade. Be sure to wear a hat and apply sunscreen generously, as the high-altitude sun is extremely intense along this stone-paved road.