it was at a dairy farm, actually, and they had it that way (at that point) for a good long time. They used it as like a visual aid or what-not for school groups that would come.
It was really cool, if not really gross.
I think that originally happened was that the cow had to have some surgery on one of its stomachs, and instead of closing it fully, for some reason they put in a plexiglass type "window" there. I'm not sure why, but it makes for fun stories! :) In fact, had I not seen the cow, alive, with my own eyes, I would not have believed it.