I visited this Cromlech at Pentre Ifan in west Wales yesterday. It was constructed in around 3500 BC, about a millenium before Stonehenge. That's even older than the combined ages of popular beat combo, the Rolling Stones.
The huge top stone seems to balance on the three uprights almost effortlessly. Seen close-up you realize that this is of course an impossible construction. Certainly one which could never stand the test of time.