How did the Egyptians build the pyramids?

The question of how the pyramids were built has not received a wholly satisfactory answer. The most plausible one is that the Egyptians employed a sloping and encircling embankment of brick, earth, and sand, which was increased in height and length as the pyramid rose; stone blocks were hauled up the ramp by means of sledges, rollers, and levers. According to the ancient Greek historian Herodotus, the Great Pyramid took 20 years to construct and demanded the labour of 100,000 men. This figure is believable given the assumption that these men, who were agricultural labourers, worked on the pyramids only (or primarily) while there was little work to be done in the fields—i.e., when the Nile River was in flood. By the late 20th century, however, archaeologists had found evidence that a more limited workforce may have occupied the site on a permanent rather than a seasonal basis. It was suggested that as few as 20,000 workers, with accompanying support personnel (bakers, physicians, priests, etc.), would have been adequate for the task.