Ancient Egypt all was a long-standing civilization in North eastern Africa. Ancient Egypt developed over three and a half millennia. It began with the incipient unification of Nile Valley polities around 3150 BC, and is conventionally thought to have ended in 31 BC when the early Roman Empire conquered and absorbed Ptolemaic Egypt as a state. Egypt is in northeast Africa bordered by Libya, Sudan, the Red Sea and the Mediterranean Sea. At one time, it was divided into Upper and Lower Egypt. Upper Egypt was the southern half nearer the rest of Africa. The Nile was the key factor in the success of ancient Egyptian civilization. The history of ancient Egypt proper starts with Egypt as a unified state, which occurred sometime around 3150 BC. The conventional Egyptian chronology is the chronology accepted during the 20th century, but it does not include any of the major revision proposals that have also been made in that time.