interior of the pyramid. The patios were unearthed in layers as far back as the Classic period (200 to 800 AD) and the beginnings of the Post-classic, during the occupation of the Olmecas Xicallancas. These structures were later reconstructed. The most important elements unearthed during this time were the Courtyard of the Altars and Edificio F (Building F). By the official end of the project in 1974, interest in the pyramid waned again as it could not be reconstructed in its entirety, like other major pyramids in Mexico. The project was abandoned, leaving only fragmentary knowledge about it. Despite the site's pre-Hispanic importance, this pyramid is relatively unknown and unstudied, especially in comparison to others in Mexico such as Teotihuacan, Chichen Itza and Monte Albán. There are a number of possible reasons for this. One is that its existence was not greatly elaborated in a publication by the Mexican government for the 1928 Congreso Internacional de Americanistas in New York. There is only one short mention of the pyramid in the entire work. However, by this time, only Bandelier had done any work on the site. Of all the work done from the 1930s to the 1950s, there was only one presentation, at the XXVII Congreso Internacional de Americanistas de México in 1939. In 1951, Marquina included Cholula in a work called Arquitectura prehispánica along with information from the various major sites of the country. However, interest waned in the Cholula site in the 1950s. One reason for this was that, at the time, it was common to reconstruct the major buildings, especially pyramids, even though these reconstructions were often exaggerated. No such reconstruction is possible with the Cholula pyramid. Most of the publications that do exist are technical field reports with few syntheses of data gathered. For this reason, it has not played a significant role in the understanding of Mesoamerica as to date. Due to the condition of the surface and the large number of artifacts just under the surface, it is not possible to reconstruct the last stage of the pyramid to what it was. Elements Excavations have resulted in about eight kilometers of tunnels inside the pyramid, which began with two in 1931 to prove that the hill was an archeological find. Within, altars with offerings, floors, walls and buried human remains from around 900 AD were discovered. Today, only about 800 meters of these tunnels