 The first two ruling dynasties of a unified Egypt set the stage for the Old Kingdom period, c. 2700–2200 BCE, which constructed many pyramids, most notably the Third Dynasty pyramid of Djoser and the Fourth Dynasty Giza pyramids.The First Intermediate Period ushered in a time of political upheaval for about 150 years.Stronger Nile floods and stabilisation of government, however, brought back renewed prosperity for the country in the Middle Kingdom c. 2040 BCE, reaching a peak during the reign of Pharaoh Amenemhat III.