The ancient Egyptian civilization developed along the fertile banks of the Nile River which provided an important water supply and flooded annually, depositing rich silt for farmland. Key cities emerged where the river contained small waterfalls called cataracts. Egypt was protected by deserts on both sides and traded extensively along the Nile and through the Mediterranean Sea and Nubia/Kush regions to the south. The society was ruled by powerful pharaohs as absolute gods over a theocratic government system and was known for its monumental pyramids, hieroglyphic writing system, and mummification practices.