The trouble is that if you dig down very deep, you might find a few things that you did not expect. this is not my photo, but was in the local newspaper when the were digging the foundations for the extension of our estate. Can you see it.
And here is a close up of what they found.
That is the sort of surprise you might get if you decide to build where there used to be the gallows. Luckily our building was already standing and they found no human remains. This is the block next to ours.