The Aztecs, as most Mesoamerican peoples, built their pyramids with a core of earth or rubble and an exterior of layered stone. In some cases, new pyramids were built over older ones. They were built steeply, with steps leading from the base to the summit.
The Great Pyramid in the Aztec capital of Tenochtitlan, which is now part of Mexico City, was built over six other pyramids. The original pyramid was constructed of earth and wood sometime in the early 14th century. Subsequent pyramids employed stone and stucco in their construction, and the temples at their peaks became more and more elaborate at each stage. Finally, the seventh and last pyramid was topped with a large and intricately sculpted ceremonial temple, the Templo Mayor, which Hernando Cortez destroyed during his conquest of the Aztecs in 1521.
The pyramids were constructed to honor the Aztec deities. The Great Pyramid had shrines to Huitzilopochtli, the god of the sun and war, as well as Tlaloc, the god of fertility and rain. At the peaks of the pyramids, the Aztecs conducted their famous human sacrifices during which still-beating hearts would be removed from the victims. Estimates of the number of victims vary greatly, but most historians agree that there were at least several thousand a year.