The Old Kingdom (c 2686—2181 BC) is usually thought to begin with the 3 dynasty. This and the following dynasty can be considered one of the pinnacles of Egyptian history. The 3 Dyn. was a formative period with many innovations, for example, the change from building in mud-brick to using stone and the beginning of pyramid construction, with the Step Pyramid at Saqqarah. At this time the basis of the future civilization of Egypt was established. The most famous ruler of this time was King Netjerikhet Zozer who reigned for 19 years. His chief of works, Imhotep, inaugurated many of the architectural innovations of the reign. Imhotep was later deified and equated with the Greek god of medicine, Asklepios, although there is no evidence that during his lifetime he was connected in any way with the medicine. Both Zozer and his predecessor Sanakhte sent expeditions to Sinai, probably in search of copper and turquoise, although in the 1 Dyn. expeditions had already been made as far as the Second Cataract and the southern boundary of Egypt extended from al-Kab to Elephantine (Aswan).
The monuments of the 4 Dyn. (c 2613—2494 BC) are better known than those of the previous period as this was the age of the pyramid builders when these vast structures were erected at Giza and nearby sites. The pyramid was only part of the complex and was intended to preserve the body of the dead king and to enable him to pass safely to the Afterworld, while the mortuary temple attached to the pyramid was for the worship of the dead king as a divine intercessor. These complexes were surrounded by many mastaba tombs where relatives, nobles, and priests were buried. The king had absolute power and the great offices of state were mainly in the hands of the royal family. But towards the end of the Old Kingdom, this power gradually became diversified. More is known about the monuments of this period than the personal and national events.
With the 5 Dyn. (C BC) the centralized power of the 2494—2345 crown declined somewhat. The earliest administrative documents, from this period, were found at Abu Sir where many of the kings, were buried. Expeditions to Libya, Nubia, and Sinai for trade were more fully recorded. The ideas of kingship were obviously modified during this time and many of the great nobles married into the royal family. The worship of the sun god Re of Heliopolis became important for the first time and, in his honor, successive kings built sun temples at Abu Ghurab. At the end of the dynasty the Pyramid Texts, a collection of rituals, spells, hymns, and myths, make their appearance on the walls of the burial chamber of Unas and continue to be represented throughout the next dynasty.
The practice of decentralization was carried still further during the 6 Dyn. ( 2345—81 BC). Much of the power passed into the hands of the great nobles who set up almost independent courts of their own in the various nomes or districts from which they drew their influence. The royal pyramids became smaller and the officials and nobles no longer felt it necessary to be buried in serried ranks surrounding the royal burial place. It was during the reign of Pepi II, who is said to have ruled for 94 years, that the central administration finally collapsed.
A series of bad harvests, low Niles, incursions of foreigners, and waning central authority ushered in the little-known period of Egyptian weakness, the 7—10 Dyns, usually known as the First Intermediate Period (c 2181—2050 ВС). During this time the central administration no longer functioned and there were several parallel local dynasties. Egypt always showed a tendency to fall apart politically if there was not a strong government.