The Great Pyramid of Khufu at Giza has a rival for size and grandeur very close at hand. Standing next to it is the pyramid of Khufu's successor Khafre, which from many angles looks bigger, having been built on slightly higher ground. Indeed, the ancient Egyptians called the Pyramid of Khafre 'The Great Pyramid' and that of Khufu 'The Pyramid which is the Place of Sunrise and Sunset'. Although a difference of only a few metres in height, The Great Pyramid is actually higher, has a shallower angle of incline than Khafre and encloses a bigger volume.

The Sphinx on the otherhand, stands alone, with no rivals either on site or elsewhere among all the sphinxes of Egypt. Truly, this is the Great Sphinx, as well as very likely being the first of the breed. The Great Sphinx started off as a knoll of rock (quarried in the course of pyramid building) at the bottom of the Giza Plateau towards the valley of the Nile.

The later sphinxes of Egypt were often installed as pairs to guard entrances to significant places, but the Great Sphinx of Giza is a one-off. And perhaps the original meaning of the Great Sphinx was too particular to be shared with another of its kind.

The damaged face of the Sphinx, smiling inscrutable smile

The Sphinx is carved out of the living rock, though parts of it have been repaired with blocks of stone. It is immediately apparent that the rock strata of which the Sphinx is made, varies from a hard grey to a soft yellowish limestone. The head is made of hard limestone of the same sort as was quarried around the pyramids. The body on the other hand, is made of poorly consolidated and therefore readily eroded limestone. The rock improves again at the base of the monument, with a return to harder (but brittle) reef-formed limestone that has allowed some carved details of the beast to remain visible after at least four-and-a-half thousand years of natural and human attrition.

In keeping with the whole Giza Plateau, these strata within the Sphinx run from east to west, in other words from the breast to the hindquarters, and north to south. The Sphinx faces due east, with the same great precision of orientation as is seen in the disposition of the Giza pyramids.

The heavily eroded Sphinx.

The monument was made from the start to point directly to sunrise. Interestingly, the face, excluding the ears is a little awry in relation to the head as a whole: the left eye is slightly higher than the right, the mouth off-centre, and the entire face slightly tilted back.

Despite the overall better quality stone of the head, the face - as is immediately apparent - is badly damaged, and not just by natural erosion. The nose is missing altogether and the eyes and the areas around them are seriously altered from their original state, as is the upper lip. Napoleon's artillerymen have been blamed for using the face of the Sphinx for target practice.

Fragments of the Sphinx beard: casts in the Cairo Museum

The alteration of the face has brought an insinuation of mood to the features, which change with the different lights (sometimes into a knowing smile). This has to be borne in mind when any attempt is made to compare the face of the Sphinx with the sculptures of various fourth Dynasty kings.

The head and face of the Sphinx certainly belong to the Old Kingdom, particularly the fourth Dynasty. The style of the headdress (known as the 'nemes' head-cloth), with its fold over the top of the head and its triangular planes behind the ears, the presence of the royal 'uraeus' cobra on the brow, the treatment of the eyes and lips all speak of that historical period.

The sculptures of kings Djedefre, Khafre and Menkaure all show the same configuration that we see on the Sphinx. Originally, the Sphinx had a plaited beard seen on many Egyptian statues. Pieces of the Sphinx's massive beard found during various excavations adorn the British Museum in London and the Cairo Museum. The beard was supported by a stone plate to the breast, parts of which have also been found.

A hole in the top of the head that is now filled in, indicates that there was once a head decoration. Depictions of the Sphinx show a crown or plumes on the top of the head, but these were not necessarily part of the original design. The top of the head is flatter, however, than later Egyptian sphinxes. Serious natural erosion of the body of the Sphinx begins below the head.

In the 1920s it was considered necessary to support the head with cement approximations of the absent parts of the head-dress, and it is these extensions that chiefly account for the altered appearance of the Sphinx's head in recent times, when compared with old photographs and drawings.

The Sphinx temple in front of the Sphinx.

Erosion below the neck does not look like scouring by wind-blown sand. In fact, so poor is the rock of the bulk of the body that it must have been deteriorating since the day it was carved. And it continues to erode before our very eyes, with spalls of limestone falling off the body of the Sphinx in the heat of every day.