I bought this item for my nephew's 7th birthday. He and his brother spent a very happy time chipping out all the little 'artefacts'. They really enjoyed it and also liked the pieces that they dug out from it.
My sister in law said that it kept them quiet for a couple of hours. It appears that it was pitched at the right age group, not too difficult, but not too easy either.
My nephew kept the little pieces and he told me that he had fun doing it - which after all was the point in buying it for him!