KHUFU'S PYRAMID was an architectural and engineering feat. To produce a structure of its immense size, phenomenal technical knowledge and organization were required. The Great Pyramid was constructed with approximately 2,300,000 limestone and granite blocks weighing from 2.5 to 50 tons each. How were these huge stones cut? Egyptologists believe that copper and bronze saws must have been used to shape the blocks, but there is no definitive evidence for this. How were the blocks transported and raised to a height of 145 meters? Although it is not know for certain how the blocks were put into place, several theories have been proposed. One theory suggests that the Egyptians constructed a straight or spiral ramp that was raised as the work proceeded. This ramp, covered with mud and water, facilitated the movement of the blocks, which were pushed (or pulled), into place. Experts estimate that as many as 100,000 slaves were needed to build the pyramid, which was erected during Khufu's reign over a period of approximately 20 years. To this day, many questions remain unanswered. And there are other mysteries.