So this is a weird question that is hard to research without people thinking you are a serial killer, but here goes: the set-up is an alternate history of Classical Rome, set about 400 CE. The religion still includes regular sacrifices, but instead of focusing on the smoke rising into the sky, it focuses on the blood soaking into the ground. So what would happen if you regularly soaked the same area (not sure on size, probably like a tennis court) with blood for 600 years? The sacrifices are usually big animals like cows, sheep, and goats with a few humans when times get bad. The rites mostly want the blood pumped out as the victim is dying- not a lot of effort to drain the maximum amount possible- and the priests are trained to slash the carotid artery. They dig up and turn the soil once a year but do not remove or replace it (unless that turns out to be really unrealistic, in which case they might have to start over from time to time).
Would it smell? What, if anything, could grow there? How much blood can soil absorb, and long does it take to dry?
How many victims at a time and how often the rites are performed are related to what I find out about the above. I don't want a situation where the soil would be constantly soupy nasty mud but I'd like the temple to be creepy.
I tried Googling variations on blood absorption, but that got me things entering the blood, not the blood entering anything else. I also checked sites and books about forensic blood analysis and some of the experiments done on the Body Farm, but none of that was helpful in determining what the ground would look like or the long-term effects of repeated soaking. Finally I checked the library for information on Aztec sacrificial rites since they were the bloodiest I could think of, but nothing on what happened with the blood.