to the practice of the Catholic Church of repurposing local religious sites. Because of the historic and religious significance of the church, which is a designated colonial monument, the pyramid as a whole has not been excavated and restored, as have the smaller but better-known pyramids at Teotihuacan. Inside the pyramid are some of tunnels excavated by archaeologists. Pyramid The pyramid consists of six superimposed structures, one for each ethnic group that dominated it. However, only three have been studied in any depth. The pyramid itself is just a small part of the greater archaeological zone of Cholula, which is estimated at . Building of the pyramid began in the Preclassic Period and over time was built over six times to its final dimensions of 300 by 315 metres on each side at the base and 25 metres tall. The base covers a total area of 94,500 square meters (1,016,669 square feet), nearly twice the size of the 53,108 square meter (571,356 square feet) base of Pharaoh Khufu's Great Pyramid of Giza. Tlachihualtepetl has the largest pyramid base in the Americas. The earliest construction phase features talud-tablero architecture that is characteristic of the region, and that became strongly associated with the great metropolis of Teotihuacan. Some of the pyramid constructions have had burials, with skeletons found in various positions, with many offerings, especially ceramics. The last state of construction has stairs on the west side leading to a temple on top, which faced Iztaccíhuatl. During the colonial period, the pyramid was severely damaged on its north side to build the Camino Real to Puebla. The west was damaged later with the installation of a rail line. Excavation history The first study of the pyramid area was done by Adolph Bandelier, a Swiss-born American archaeologist with an interest in Mexico. He arrived at Cholula in 1881 and published his findings about the site in 1884. Most of Bandelier's work involved the unearthing of various burials in the area around the pyramid, principally collecting skulls, which was standard practice at the time. Many of these wound up in storerooms in U.S. museums. Bandelier also took the first precise measurements of the structure, made some headway into how it was constructed and worked on domestic structures that coincide with the pyramid. Bandelier was also the first to make precise field notes at the site and the earliest plan of the site. Bandelier also