Aztec temples were typically expanded by building over prior ones, using the bulk of the former as a base for the latter, as later rulers sought to expand the temple to reflect the growing greatness of the city of Tenochtitlan. Therefore, digging down through this temple takes us back in time. The first temple was begun by the Aztecs the year after they founded the city, and the temple was rebuilt six times. All seven stages of the Templo Mayor, except the first, have been excavated and assigned to the reigns of the emperors who were responsible for them.