1) In order to be the tomb of the king where the body is mummified and put in a   box then buried in a room known as king's chamber that is always under the ground. The purpose of this mummification is their belief that there is an eternal life after death and because of the resurrection food and water were put in these tombs and some fearful and awful shapes have been carved on its walls as a source for fear and awe.

2) The ancient Egyptian chose the shape of pyramid in building their tombs because they would resist the natural calamities such as earthquakes and strong storms.