Tiantan functioned very much like an Aztec temple, except they substituted humans for livestock (reminds me of my IAS 45 teacher's suggestion that perhaps the reason for human sacrifice in the new world is a lack of big, dumb animals you can easily lead to slaughter). Until the beginning of the 20th century, these animals would be burned in cauldron's outside the temple as a way of worshipping heaven.
EAP China! Robert Klein