(Mexico-Tenochtitlan, the capital of Aztec empire, at its height being inhabited by 200,000 people in the center and over a million in the suburbs, more than London of the time. Only Paris, Venice and Constantinople were larger at the time)
To me, this was interesting (especially the part marked below in bold) for a number of reasons. From the Wikipedia article.
* * *Sacrifice was a common theme in Mesoamerican cultures. In the Aztec "Legend of the Five Suns", all the gods sacrificed themselves so that mankind could live. Some years after the Spanish conquest of Mexico, a body of Franciscans confronted the remaining Aztec priesthood and demanded, under threat of death, that they desist from their murderous practice. The Aztec priests defended themselves as follows:
Life is because of the gods; with their sacrifice they gave us life [...]. They produce our sustenance [...] which nourishes life.What the Aztec priests were referring to was a central Mesoamerican belief: that a great, on-going sacrifice sustains the Universe. Everything is tonacayotl: the "spiritual flesh-hood" or on earth. Everything —earth, crops, moon, stars and people— springs from the severed or buried bodies, fingers, blood or the heads of the sacrificed gods. Humanity itself is macehualli, "those deserved and brought back to life through penance". A strong sense of indebtedness was connected with this worldview. Indeed, nextlahualli (debt-payment) was a commonly used metaphor for human sacrifice, and, as Bernardino de Sahagún reported, it was said that the victim was someone who "gave his service".
Human sacrifice was in this sense the highest level of an entire panoply of offerings through which the Aztecs sought to repay their debt to the gods. Both Sahagún and Toribio de Benavente (also called "Motolinía") observed that the Aztecs gladly parted with everything: burying, smashing, sinking, slaying vast quantities of quail, rabbits, dogs, feathers, flowers, insects, beans, grains, paper, rubber and treasures as sacrifices. Even the "stage" for human sacrifice, the massive temple-pyramids, was an offering mound: crammed with treasures, grains, soil and human and animal sacrifices that were buried as gifts to the deities. Adorned with the land's finest art, treasure and victims, these temples had become buried offerings under new structures every half a century.
The sacrifice of animals was common, a practice for which the Aztecs bred dogs, eagles, jaguars and deer. Objects also were sacrificed by being broken and offered to the gods. The cult of Quetzalcóatl required the sacrifice of butterflies and hummingbirds.
Self-sacrifice was also quite common; people would offer maguey thorns, tainted with their own blood and, like the Maya kings, would offer blood from their tongue, ear lobes, or genitals. Blood held a central place in Mesoamerican cultures. The Florentine Codex reports that in one of the creation myths Quetzalcóatl offered blood extracted from a wound in his own genital to give life to humanity. There are several other myths in which Nahua gods offer their blood to help humanity.
Common people would offer maguey thorns with their blood. Lloyd deMause has argued that, like present-day self harmers, the Aztecs also practiced bloodletting from cuts made with obsidian knives or bone needles on fleshy parts of the body, like earlobes, lips, tongue, chest and calves. This was considered private and a personal act of penitence toward the gods. The thorns and later placed in an adoratorium.
[This part was especially interesting:]
Much like the role of sacrifice elsewhere in the world, it thus seems that these rites functioned as a type of atonement for Aztec believers. Their sacrificial hymns describe the victim as 'sent (to death) to plead for us,' or 'consecrated to annul all sin. '(Duran, Book of the Gods and Rites, 232). In one such poem, a warrior-victim announces that 'I embrace mankind... I give myself to the community.'(MSS Romance de Los ... Folio 27r).
Aztec society viewed even the slightest tlatlacolli ('sin' or 'insult') as an extremely malevolent supernatural force. For instance, if an adulterer were to enter a house, it was believed that all turkey chicks would perish from tlazomiquiztli, 'filth-death' (Sahagun Bk. 5: 29: 191-192). To avoid such calamities befalling their community, those who had erred punished themselves by extreme measures such as slitting their tongues for vices of speech or their ears for vices of listening, and 'for a slight [sin they] hanged themselves, or threw themselves down precipices, or put an end to themselves by abstinence' (Motolinia, History of the Indies, 106-107). In Classic Nahuatl (the Aztec language) the verbal form ni-c-yecoa, 'I sin', is closely related to ni-c-ye.coa, 'I finish it.' It was believed that error of any sort could quite literally 'finish' or 'ruin' everything (Francisco Clavigero, Historia antiqua de México, 7). This seems to have given Aztec society a heavy dependence on extremely violent 'penance,'of which human sacrifice was considered one form (as already mentioned, human sacrifice was often called 'penance').
A great deal of cosmological thought seems to have underlain each of the Aztec sacrificial rites. By far the most common form of human sacrifice was heart-extraction, and this seems to have related to the Aztec belief that the heart(tona) was both the seat of the individual and a fragment of the Sun's heat (istli). To this day, the Nahua consider the Sun to be a heart-soul (tona-tiuh) 'round, hot, pulsating'(Alan Sandtrom, Corn is Our Life, 1991, 239-240). It seems that in the Aztec view, humanity's 'divine sun fragments' were considered 'entrapped' by the body and its desires:
Where is your heart? You give your heart to each thing in turn. Carrying, you do not carry it... You destroy your heart on earth (Nahua poem in Irene Nicholson, Firefly in the Night, 156 & 203).
Heart-extraction was viewed as a means of liberate istli and reunite it with the Sun, as aptly depicted in Codex Magliabechiano, Folio 70 (illustrated in this section), wherein a victim's transformed heart flies Sunward on a trail of blood.
Finally, it should be noted that according to the Aztec (and Mesoamerican) world-view, the circumstances in which people died determined the type of afterlife they enjoyed. The Aztecs had meticulously organised death into several types, which each led to specific 'heavenly' and 'underworld' levels. In the levels Sahagun records, passing away quietly at home was the lowest, as it required the unfortunate soul to undergo numerous torturous trials and journeys, only to culminate in a sombre underworld. By contrast, what the Aztecs termed 'a good death' was sacrifice, war (which usually meant sacrifice) or — in the case of women — death whilst giving birth. This kind of end procured for the deceased the second-highest heaven (death in infancy being the highest). Persons who had died sacrificially or in war were called 'the God-dead' (Teo-micqui ) and were said to 'go pure... live hard by, nigh unto the Sun... [who] always forever ... rejoice ... [since] the House of the Sun is ... a place of joy (Sahagun Bk 6: 21).
The cycle of fifty-two years was central to Mesoamerican cultures. The Nahua's religious beliefs were based on a great fear that the universe would collapse after each cycle if the gods were not strong enough. Every fifty-two years a special New Fire ceremony was performed. All fires were extinguished and at midnight a human sacrifice was made. The Aztecs waited for the dawn. If the Sun appeared it meant that the sacrifices for this cycle had been enough. A fire was ignited on the body of a victim, and this new fire was taken to every house, city and town. Rejoicing was general: a new cycle of fifty-two years was beginning, and the end of the world had been postponed, at least for another 52-year cycle. (A similar ceremony is still practiced by small indigenous groups, but without human sacrifice.) The ceremony was older than the Aztecs. While originally it was believed it was a matter of luck to survive, the Aztecs thought that constant sacrifice through the fifty-two year cycle could postpone the end.
According to Miguel León-Portilla, Tlacaelel reformed the original Nahua religion and the Aztecs viewed themselves as the main representatives for feeding the gods. This gave them a new sense of identity, from "people without face" as they were called by hostile neighbours, to the people in charge of the existence of the universe. Thus they began to call themselves "The people of the sun". Other researchers dispute León-Portilla's perspective, pointing to the relative lack of primary sources.