The Calzada de los Muertos (Avenue of the Dead) is actually made of a series of walled plazas. Discoloration on the lower plaza walls, makes it apparent that the plazas were flooded 3 to 4 feet with water, making the the long expanse of the avenue a huge reflecting pool to enhance the views from the tops of the pyramids.

Again looking north at the Pyramid of the Moon you can see how the Avenue of the Dead is constructed of many, many plazas. You have to walk up and down stairs into and out of them on your stroll up the avenue.