What is more interesting to me is both Civilizations decided that a road should go through the area, typically roads served some commercial or military purpose that apparently both decided needed that huge an expenditure of manpower to build.
There’s an old African saying, “where you find a man, there you will find a road.” There’s probably a pretty old roadbuilding tradition, and as in all cultures, the quality of the roadways varied quite a bit. Obviously those big-assed rocks at Stonehenge didn’t get there without some kind of A) trackway and B) political cooperation or authority over a nice big swath.