This was really bugging us both, so son got a shovel out of the garage and started digging - carefully to avoid the live electric lines, even tho they are encased in PVC. About 6 inches down, he hit cement. I thought maybe it was just part of a broken cinder block, so he went to an entirely different location within the square and dug another hole - hits cement again. So we really had to reach back in time and search memories and put the pieces together.

Well - we found a partial answer and Bonny had it right to a point - but it still doesn't explain that this is the first time that it has ever happened. We got down to serious thinking, and remembered that there had been another shed in that area after the first one was demolished, and it sat on a cement pad. When that one got demolished and yet another bigger one put in, it was just installed over the old cement pad. That shed stood for many years when it ultimately got torn down when the garage went in. The cement pad was never broken up and hauled away, and soil was just piled on top, dozed level and grass planted.

So it seems there indeed is a cement pad under this square. But since it has been buried there for the past 6+ years, why didn't the grass die off 6 years ago?? Why now?? Every year it has been just as green as all the other grass around it, and it can't be said it's because of drought conditions, since we're far from that!!!

Well, at least now I know it wasn't a square space craft ~~~~~ was it?

Mystery half solved.