Ancient Egypt was an ancient civilization in eastern North Africa, concentrated along the lower reaches of the Nile River in what is now the modern nation of Egypt. The civilization began around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh, and it developed over the next three millennia. Its history occurred in a series of stable periods, known as kingdoms, separated by periods of relative instability known as Intermediate Periods. After the end of the last kingdom, known as the New Kingdom, the civilization of ancient Egypt entered a period of slow, steady decline, during which Egypt was conquered by a succession of foreign powers. The rule of the pharaohs officially ended in 31 BC when the early Roman Empire conquered Egypt and made it a province.