The Great Pyramid of Gizeh in Egypt is a true mystery. It is generally known as "the Pyramid of Khufu (Cheops) - built in 20 years of his reign by thousands of workers, equipped with ropes and copper tools - to serve as Khufu's tomb".
However,
- there is no sign or artefact that tells us that the pyramid ever was a burial place.
- no solid proof exists that Khufu built this pyramid. The drawings in the chambers above the King's Chamber that relate to his name, were never claimed by the discoverer of these chambers, H. Vyse (see Vyse).
- twenty years to built a pyramid that consists of about 2 million blocks requires a delivery speed of one block every 5 minutes, an extremely sophisticated logistic achievement which has never been repeated ever since.
- essential parts of the pyramid are made of granite, a hard rock material that can not be worked with copper tools.
- advanced cylindrical drill techniques were applied in hard stone. Clear evidence was already provided by extensive research by W.F. Petrie in 1883, (Petrie).
- the chambers above the King's Chamber are not relieving chambers as is repeatedly stated. There is no technical analysis that supports this conception. Moreover, the lower chambers that bear even more weight - i.e. the Queen's Chamber and the King's Chamber in the Second Pyramid - have no such 'relieving chambers'.
- the King's Chamber has suffered destructing forces by which it is out of joint. Restoration materials proof that the restoration already took place in ancient times. What caused this destruction that only effected the King's Chamber and not the Queen's Chamber and the third chamber is unknown. From an engineering point of view, resonance in the King's Chamber seems a logical explanation. 
- formal scientific research has proven that this pyramid is more than 300 years older than the time that pharaoh Cheops lived
- Perhaps this pyramid was some sort of machine. This idea has been explored by C. Dunn, see (Dunn).