The Spanish invaders were shocked to find that the Aztecs carried out huge numbers of human sacrifices at their temples.
The scale of the killings has long been a matter of controversy as the Spanish may have exaggerated the numbers killed to make the Aztecs appear more barbaric.
Sacrifice was a central focus of religion in Central America. People would often stab themselves with thorns in their tongues, ears or even genitalia to offer the blood to the gods. As for human sacrifice, some victims volunteered for the good of the community or to atone for a sin, but most were prisoners of war or criminals.
The Spanish records relate mostly to the Aztec capital of Tenochtitlan, where sacrifices took place 18 times every year, with around 60 victims each time. A human sacrifice was dedicated to one of the gods, so the form of sacrifice varied accordingly.
The god Tlaloc, for example, demanded that children have their throats cut, and to please Chicomecoatl, a girl was beheaded. Huitzilopochtli preferred to have the beating hearts of men cut out and placed in front of his statue, while the severed head was put on a rack on the temple walls.
It is possible that around 20,000 people were sacrificed a year in the Aztec Empire. Special occasions demanded more blood – when a new temple to Huitzilopochtli was dedicated in 1487, an estimated 80,400 people were sacrificed.