The great pyramid was built during the reign of Khufu, 2nd king of the fourth dynasty (2,720-2,560 BC). It stands on the Giza plateau nearby Cairo and is the biggest pyramid in the world. It measures 230 m (756 ft) on each side of its base and originally measured 147 m (482 ft) high. Beginning in the 10th century AD the entire Giza complex served as a source of building materials for the construction of Cairo; as a result, all three pyramids were stripped of their original smooth outer facing of limestone.
The core masonry consists of large blocks of local limestone taken from the nearby quarries and built around and over a rocky knoll. The size of the knoll cannot be determined, since it is completely covered by the pyramid. The entrance to the pyramid is in the center of the northern face. It is located in the thirteenth course of masonry from the base. This entrance has a pointed roof formed of massive slabs of local limestone and opens into a long steeply descending passage. From there a 36 meters long ascending passage leads to a 35 meters long horizontal passage that leads to the so called 'Queen's chamber'. This chamber measures 5.2 by 5.7 meters and the maximum height of its pointed roof is about 15 meters. The north and south walls each have a small hole a few centimeters square about 1 meter from the floor. These lead into narrow channels that originally opened on the exterior of the pyramid. At the juncture of the ascending and horizontal passage is an opening of a shaft which descends to a depth of 60 meters. It opens into the lower part of the descending passage, close to the unfinished, underground chamber, and is believed to have been an escape shaft for the workmen who filed the ascending passage with huge stones after the king's funeral.
From the horizontal passage the Grand Gallery, which leads to the king's chamber, starts. It is 47 meters long and 8.5 meters high, and has a corbelled roof. In the center of the floor is a sunken ramp about 60 centimeters deep. The Grand Gallery ends in a horizontal granite passage which serves as an antechamber. It measures 8.4 meters long and 3.1 meters high, and has slots for three portcullises. Beyond the antechamber is the so-called 'King's Chamber' which is lined, roofed and paved with red granite. It measures 5.2 by 10.8 meters and is 5.8 meters high. Its flat roof is formed of nine monolithic slabs of granite. The northern and southern walls each have an 'air channel', one of which is open to the outside. The Pyramid can be seen to have about two hundred level courses of squared stones. The layers all have a different thickness ranging between approximately 50 and 145 centimeters. The average block size is about 1 cubic meter.
On the Khufu pyramid, all the casing elements were removed in the 14th century. The few casing stones which do remain in the Great Pyramid all lie in the 1.5 meter thick bottom course and cannot be representative of the stones which would have been used in the higher parts of the construction. The only examples of face work such as this which remain are those on the pyramids at Meidum, Dashur andGiza.