<P> The Great Pyramid consists of an estimated 2.3 million blocks which most believe to have been transported from nearby quarries . The Tura limestone used for the casing was quarried across the river . The largest granite stones in the pyramid, found in the "King's" chamber, weigh 25 to 80 tonnes and were transported from Aswan, more than 800 km (500 mi) away . Traditionally, ancient Egyptians cut stone blocks by hammering into them wooden wedges, which were then soaked with water . As the water was absorbed, the wedges expanded, causing the rock to crack . Once they were cut, they were carried by boat either up or down the Nile River to the pyramid . It is estimated that 5.5 million tonnes of limestone, 8,000 tonnes of granite (imported from Aswan), and 500,000 tonnes of mortar were used in the construction of the Great Pyramid . </P> <P> At completion, the Great Pyramid was surfaced by white "casing stones"--slant - faced, but flat - topped, blocks of highly polished white limestone . These were carefully cut to what is approximately a face slope with a seked of 51⁄2 palms to give the required dimensions . Visibly, all that remains is the underlying stepped core structure seen today . In AD 1303, a massive earthquake loosened many of the outer casing stones, which were then carted away by Bahri Sultan An - Nasir Nasir - ad - Din al - Hasan in 1356 to build mosques and fortresses in nearby Cairo . Many more casing stones were removed from the great pyramids by Muhammad Ali Pasha in the early 19th century to build the upper portion of his Alabaster Mosque in Cairo not far from Giza . These limestone casings can still be seen as parts of these structures . Later explorers reported massive piles of rubble at the base of the pyramids left over from the continuing collapse of the casing stones, which were subsequently cleared away during continuing excavations of the site . </P> <P> Nevertheless, a few of the casing stones from the lowest course can be seen to this day in situ around the base of the Great Pyramid, and display the same workmanship and precision that has been reported for centuries . Petrie also found a different orientation in the core and in the casing measuring 193 centimetres ± 25 centimetres . He suggested a redetermination of north was made after the construction of the core, but a mistake was made, and the casing was built with a different orientation . Petrie related the precision of the casing stones as to being "equal to opticians' work of the present day, but on a scale of acres" and "to place such stones in exact contact would be careful work; but to do so with cement in the joints seems almost impossible". It has been suggested it was the mortar (Petrie's "cement") that made this seemingly impossible task possible, providing a level bed, which enabled the masons to set the stones exactly . </P> <P> Many alternative, often contradictory, theories have been proposed regarding the pyramid's construction techniques . Many disagree on whether the blocks were dragged, lifted, or even rolled into place . The Greeks believed that slave labour was used, but modern discoveries made at nearby workers' camps associated with construction at Giza suggest that it was built instead by tens of thousands of skilled workers . Verner posited that the labour was organized into a hierarchy, consisting of two gangs of 100,000 men, divided into five zaa or phyle of 20,000 men each, which may have been further divided according to the skills of the workers . </P>

What is special about the pyramids of giza