Speaking of Stonehenge, someone sent this youtube link to me the other day along the same lines as this thread.
I saw it about a month ago. Truly remarkable the way this one guy, using stones, sticks and rope and simple techniques of leverage and gravity can demonstrate how to move a 19,000 lb block horizontally and vertically by himself.
He thinks Stonehenge could have been built this way without a lot of manpower and the Pyramids as well.