Egypt is located in northeast Africa and is divided into two parts by the Nile River, which flows north from south of the Mediterranean Sea to the Mediterranean. The Old Kingdom from 2650-2134 BC was a rich and creative period in Egyptian history, while the Middle Kingdom from 2055-1650 BC saw rule first from Thebes and then from El-Lisht. Ahmose began the expulsion of the Hyksos invaders around 1522 BC, starting a period of conquest and prosperity. Cheops was the second king of the 4th dynasty and built the Great Pyramid of Giza, while Djoser was an earlier king also known as Netjerikhet.