The racks were known as “tzompantli” and they were used by the Aztecs to display the severed heads of sacrificial victims, which were exhibited for all to see on vertical posts. The skulls were suspended horizontally by the use of wooden poles push through the sides.

According to Eduardo Matos, the skull rack was a “show of might” used by the Aztecs to impress friends and enemies alike. They were invited into the city where they would be cowed into passivity by the grisly display of huмคห heads, several of them in advanced stages of decomposition. Such racks were often depicted in paintings and written texts from the early colonial period, however this discovery is different in that part of the platform where the heads were displayed was itself made from rows of skulls fixed together with mortar. The platform formed a rough circle with an open space in the centre and the skulls looking inward into the open space. However, the archaeologists don’t yet know what was in this central open space.

“There are 35 skulls that we can see, but there are мคหy more in underlying layers” said archaeologist Raul Barrera, speaking to Associated Press (AP) . He added that as the archaeologists continue to dig downwards they will probably discover a lot more.

Barrera also said that at least one Spanish writer had described the mortared-together skulls, following the conquest of the Aztec kingdom, but no such discovery has been made – until now that is. Susan Gillespie, an archaeologist from the University of Florida, said that she doesn’t know of any other instances of skulls being used to make such a structure.

Archaeologists began to uncover the structure from February this year, on the western side of what had once been the Templo Mayor complex. It was located under the floor of a three-story colonial era house, which meant that archaeologists had to work carefully suspended on their stomachs on a wooden platform in narrow excavation wells six feet under the floor level.

Excavations carried out at the site since 1914 have indicated the possible presence of an Aztec ceremonial site, which fits accurately the descriptions of the Spaniards. According to Gillespie, other racks have been discovered which are better described as ‘head racks’ on the basis that the severed heads were displayed shortly after each execution. However, archaeologists have been searching for a long т¡мe for the main rack.

“They’ve been looking for the big one for some т¡мe, and this one does seem much bigger than the already excavated one” Gillespie wrote in her notes. “This find both confirms long-held suspicions about the sacrificial landscape of the ceremonial precinct, that there must have been a much bigger tzompantli to curate the мคหy heads of sacrificial victims as a kind of public record or accounting of sacrifices.”

The Templo Mayor, meaning ‘Great Temple’, was a major Aztec temple dating from the Late Postclassic period of Mesoamerica. A typical Aztec sacrificial ritual would involve the victims being forced by four priests to lie down on a slab. Another priest would then open up each person’s abdomen with a flint knife, exposing the diaphragm. The priest would then tear out the victim’s heart while it was still beating. This would be placed in a bowl held by a statue of a god, probably depicting Mictlantecuhtli, the Aztec god of death. The victim’s body would be thrown down a flight of steps descending the side of the pyramid on which the temple stood. It would finally come to rest on a terrace at the base. During the reconsecration of the Great Pyramid of Tenochtitlan in 1487, the Aztecs boasted that they had slaughtered 80,400 prisoners over the course of four days, although this is believed to be an exaggeration. However, in 2012 archaeologists discovered 50 skulls and 250 jaw bones in the ruins of Tenochtitlan beneath Mexico City, testifying to the gruesome practices of the Aztecs.