Don't count it out yet! The Cromlech will be rebuilt on the other side of Monsaraz and become an easy and fast attraction for the entertainment of travellers on the way to the hill-village.
Over 136 sites were recorded last century by the Leisner couple in their Megalithic Iberia volumes only in an area of 100 square km around the Hill Of Monsaraz. I have seen a few, very ruined passage graves, still visible in the area to be flooded. Latest estimates are that about 200-300 archaeological sites will be gone, but that is to be expected in such an ancient area. If it helps to make you feel better, just as much is on the other side, and I am only talking about this 100 square km area round the hill.
And to add to your bulky account of stone age information, some very ancient Old Stone Age engravings have been found on the banks of the River Guadiana.