This picture was taken this summer in the south of France, in case it’s relevant. The area was on the side of a mountain (near a village) and had olive trees all around. Any idea?
Is it? It's really hard to see how far down that is, I was thinking something like 2.5m diameter at least, which sounds like it could be a brickwork silo? I dunno, I'm not a siloologist at all, just going off things I've seen standing around.