The scale of the skull rack is massive - there’s a graphic in the article that has to be seen to be believed.

Some conquistadors wrote about the tzompantli and its towers, estimating that the rack alone contained 130,000 skulls. But historians and archaeologists knew the conquistadors were prone to exaggerating the horrors of human sacrifice to demonize the Mexica culture. As the centuries passed, scholars began to wonder whether the tzompantli had ever existed.

Archaeologists at the National Institute of Anthropology and History (INAH) here can now say with certainty that it did. Beginning in 2015, they discovered and excavated the remains of the skull rack and one of the towers underneath a colonial period house on the street that runs behind Mexico City's cathedral. (The other tower, they suspect, lies under the cathedral's back courtyard.) The scale of the rack and tower suggests they held thousands of skulls, testimony to an industry of human sacrifice unlike any other in the world.