The Great Pyramid of Giza was built for King Khufu (known to the Greeks as Cheops) some four and a half thousand years ago. It is a structure of such awe-inspiring dimensions that many people across the centuries have found it hard to credit its creation to human beings. And even harder to realise that these human beings had not fully mastered the use of, say, the simple rope pulley, let alone explosives, mechanical diggers, power drills, cranes and helicopters.A few minor points of ambiguity remain: for example, though all the experts agree that some form of giant ramp must have been used in building the higher levels, it has not been settled what kind of ramp this was. For the most part, though, everyone who has studied the matter seriously now agrees that the Pyramid was built over the course of some 20 or so years by a work force of some 20,000 people.