<P> For the Great Pyramid of Giza, most of the stone for the interior seems to have been quarried immediately to the south of the construction site . The smooth exterior of the pyramid was made of a fine grade of white limestone that was quarried across the Nile . These exterior blocks had to be carefully cut, transported by river barge to Giza, and dragged up ramps to the construction site . Only a few exterior blocks remain in place at the bottom of the Great Pyramid . During the Middle Ages (5th century to 15th century), people may have taken the rest away for building projects in the city of Cairo . </P> <P> To ensure that the pyramid remained symmetrical, the exterior casing stones all had to be equal in height and width . Workers might have marked all the blocks to indicate the angle of the pyramid wall and trimmed the surfaces carefully so that the blocks fit together . During construction, the outer surface of the stone was smooth limestone; excess stone has eroded as time has passed . </P> <P> The pyramids of Giza and others are thought to have been constructed to house the remains of the deceased Pharaohs who ruled over Ancient Egypt . A portion of the Pharaoh's spirit called his ka was believed to remain with his corpse . Proper care of the remains was necessary in order for the "former Pharaoh to perform his new duties as king of the dead .". It's theorized the pyramid not only served as a tomb for the Pharaoh, but also as a storage pit for various items he would need in the afterlife . "The people of Ancient Egypt believed that death on Earth was the start of a journey to the next world . The embalmed body of the King was entombed underneath or within the pyramid to protect it and allow his transformation and ascension to the afterlife ." </P> <P> The work of quarrying, moving, setting, and sculpting the huge amount of stone used to build the pyramids might have been accomplished by several thousand skilled workers, unskilled laborers and supporting workers . Bakers, carpenters, water carriers, and others were also needed for the project . Along with the methods utilized to construct the pyramids, there is also wide speculation regarding the exact number of workers needed for a building project of this magnitude . When Greek historian Herodotus visited Giza in 450 BC, he was told by Egyptian priests that "the Great Pyramid had taken 400,000 men 20 years to build, working in three - month shifts 100,000 men at a time ." Evidence from the tombs indicates that a workforce of 10,000 laborers working in three - month shifts took around 30 years to build a pyramid . </P>

What is the purpose of the great pyramids of giza