Excerpts from Books and Wikipedia
"With the rise of the Old Kingdom around 2700 B.C., rulers of the 3rd dynasty began building lofty tombs in the hope that their spirits would ascend to heaven after death. The earliest of these monuments were step pyramids, resembling ziggurats. During the 4th dynasty, royal architects refined the design by erecting gigantic smooth-sided pyramids. The supreme example is the 482-foot-high Great Pyramid at Giza built by Pharaoh Khufu, who reigned around 2550 B.C. . . . Guarding the entire complex was the cat-like Sphinx, bearing the face of Khufu's son Khafre." [National Geographic Almanac, p. 51-2] 3rd Dynasty: Djoser (2667-2648 BC); Step Pyramid at Saqqara constructed 2667-2648 BC; 4th Dynasty: Khufu (Cheops) constructed Great Pyramid of Giza; "The fact that Snefru [r. 2613-2589 BC] was able to complete one pyramid and build two more suggests that Egypt was now even richer, and more peaceful, and more subject to the authority of the pharaoh, than ever before." [Bauer: Ancient Worlds, p. 84]