From Wikipedia

Aztec Temple Of Blood

Human sacrifice was an aspect of historical Aztec culture/religion, although the extent of the practice is debated by scholars. The Spaniards who first meet the Aztecs explicitly stated in their writings that human sacrifice was widely practiced in Mesoamerica. For example, Bernal Díaz's The Conquest of New Spain includes eye-witness accounts of the remains of sacrificial victims. In addition, there are a number of second-hand accounts of human sacrifices written by Spanish friars, told to them by native eye-witnesses.

Presently, scholars largely accept that human sacrifice was practiced in the Aztec Empire as well as throughout pre-Columbian Mesoamerica. Since the late 1970s, excavations of the offerings in the Great Pyramid of Tenochtitlan, Teotihuacán's Pyramid of the Moon and other archaeological sites have provided physical evidence of human sacrifice among the Mesoamerican peoples.

A wide number of interpretations of the Aztec practice of human sacrifice have been proposed by modern scholars, both with regards to its religious and social significance. For example, one theory that has been widely discredited is that the Mesoamerican diet was lacking protein and that cannibalism of sacrificial victims was a necessary part of the Aztec diet. Other theories link the practice to special socio-psychological factors or see it as a political tool. Most Mesoamerican scholars, however, see it as a part of the millennia-long cultural tradition of human sacrifice in Mesoamerica.

Human sacrifice among pre-Columbian indigenous populations is a controversial topic. The discussion of human sacrifice is also tied with the classic conflict between viewing indigenous peoples as either "noble savages" or "primitive barbarians" also within modern scholarship, where some scholars tend to romanticize the description of human sacrifice while others tend to exaggerate it.