According to the new research detailed
in Science, captives were first taken to the city's Templo Mayor, or great temple, where priests removed their still-beating hearts.
The bodies were then decapitated and priests removed the skin and muscle from the corpses' heads.
Large holes were carved into the sides of the skulls, allowing them to be placed onto a large wooden pole.
They were then placed in Tenochtitlan's tzompantli, an enormous rack of skulls built in front of the Templo Mayor, a pyramid with two temples on top.