On the way back we passed what appeared to be a quarry of some sort. It was quite strange. From a distance you could see a tell-like mound with crumbling buildings on top not unlike a Ksar. Close up it was a mound of mis-shapen boulders.
It was difficult to see how they had been built up as the mound sat on the flat of the Sousse valley. Nearby were a large number of dressed stone blocks which suggested that the area was a quarry but it was difficult to see where the stone came from as there was no hole excavated and no hill to be bitten into just the valley floor.
The anti-atlas are a few kilometres behind the dressed stone blocks say 1m-1.5m square.