The Nile River was essential to the development of ancient Egyptian civilization, providing fertile land for agriculture. Its predictable annual flooding enriched the soil and allowed Egyptians to develop permanent settlements along its banks. The river also served as the primary transportation route, connecting all parts of Egypt. Cut off from outside influences by deserts, Egyptian culture evolved uniquely with a focus on religion, the pharaoh's divine rule, and grand architecture like the pyramids and temples built from stone. While the exact methods are unknown, it is believed the pyramids were constructed using ramps and lever systems requiring a large workforce of laborers and artisans. Egyptian society was highly stratified but opportunities existed for social mobility through professions like scribe.