During three years of careful excavation, the archaeologists found that over 140 children, between the ages of 5 and 14 years of age, along with 200 young llamas were ritually sacrificed and buried on a bluff overlooking Peru's northern shoreline, in the shadow of what was then the capital city of Chan Chan, a large adobe city in the Moche Valley of present-day Trujillo, Peru. The next largest was the ritual murder of 42 children in Templo Mayor in the Aztec capital of Tenochtitlán, now Mexico City.
At the time of the supposed sacrifice, the area was under the little-known Chimú Empire.
Describing the finding as both "surprising" and "shocking", John Verano from Tulane University in New Orleans, one of the leads on the project, told IFLScience it reveals "a form of child sacrifice unimaginable until this discovery".
Archeologist have been exploring the dig site known as "Huanchaquito-Las Llamas" since 2011 when locals found human remains there.
A lot of them were aged eight to 12, disclosed the archaeologists, who note that the children were mostly buried facing west, towards the sea.
After closely examining the remains of the children, the archeologists discovered that there were evidence of cuts to the sternum as well as rib dislocations, which suggest the victims' chests might have been cut open and pulled apart in order to facilitate ancient rituals like the removal of the heart.
In this 2011 photo, archaeological students clean the remains of children and young llamas in the fishing town of Huanchaquito, Trujillo. The llamas were all less than 18 months old and were buried facing east, toward the Andes. Items found in the burials, such as ropes, are radiocarbon dated to between 1400 and 1450, toward the end of the Chimu Empire's rule, before they were conquered by the Incas.
"There are no other examples of child sacrifices anywhere in the world that compares to the magnitude of this Chimú event", Verano says.
From the footprints, it appears that the children and llamas were led in a single line and sacrificed one after the other.
"There's this idea that ritual killing is contractual, that it's performed to get something from supernatural deities", Klaus said.
The researchers are now trying to figure out why these children were sacrificed.
"When people hear about what happened and the scale of it, the first thing they always ask is 'why?' " Prieto told National Geographic. Prieto said, explaining that a layer of mud was caked around the bodies, suggesting evidence of severe rains from El Nino in a usually dry area.
Mr Quilter is part of a team which will analyse DNA from the children's remains to see if they were related and to find out where they came from.