Ancient Egypt was unified around 3100 BCE by King Menes, who combined Upper and Lower Egypt. It was then divided into three major time periods: the Old Kingdom saw the building of pyramids at Giza; the Middle Kingdom was a time of culture and trade until invaders destroyed it; and the New Kingdom became an empire through conquest but was later invaded. Famous pharaohs included Hatshepsut, Thutmose III, and Ramses II.