Digging in Mexico City has revealed an altar built from human bones, and skulls showing evidence of sacrifice to the Aztec gods.
The three skeletons date from around 1400, before Cortes and his conquistadors overran the city then known as Tenochtitlan, and overthrew Emporer Montezuma.
The powerful Aztec empire captured prisoners and sacrificed them in a ritual which involved slicing open their chests and pulling out the beating hearts. Among the many Aztec gods were those who demanded the flow of human blood just to make the sun rise.
Holes in the sides of the skulls indicate that they had been used in a skull rack (tzompantli), a rod upon which heads were strung for display outside temples and at other important locations.
Aztec Bones discovered January 2014: The Times
Past gruesome discoveries at the Mexico City site: Daily Mail