676 human skulls was unearthed under the Metropolitan Cathedral of Mexico City. These were the first evidence found that the Aztecs sacrificed women and children that they captured from other nations. As of 2017, the bottom of the pile of skulls still hasn't been reached by excavations.
https://www.reuters.com/article/us-mexico-archaeology-skulls/tower-of-human-skulls-in-mexico-casts-new-light-on-aztecs-idUSKBN19M3Q6
ref - https://www.reddit.com/r/todayilearned/comments/9chmni/til_676_human_skulls_was_unearthed_under_the/
https://www.reuters.com/article/us-mexico-archaeology-skulls/tower-of-human-skulls-in-mexico-casts-new-light-on-aztecs-idUSKBN19M3Q6
ref - https://www.reddit.com/r/todayilearned/comments/9chmni/til_676_human_skulls_was_unearthed_under_the/