Outside our back door we have brick paving. Next to a wall (on the other side of our living room), something has dug out a hill of rubble/dust and there is a hole the size of my fist (petite lady here!). There appears to be a bit of soil in it as well so I don't know how solid the foundations are, but we have LOTS of mole hills in our garden. I noticed the hole when I moved plant pots away from the wall. Help, it's making me feel all itchy!