By about 6000 BC the Neolithic culture rooted in the Nile Valley. A unified kingdom was founded circa 3150 BC by King Menes, giving rise to a series of dynasties that ruled Egypt for the next three millennia. Egyptian culture flourished during this long period and remained distinctively Egyptian in its religion, arts, language and customs. The first two ruling dynasties of a unified Egypt set the stage for the Old Kingdom period, c.2700−2200 BC., famous for its many pyramids, most notably the Third Dynasty pyramid of Djoser and the Fourth Dynasty Giza Pyramids.