Final answer:
Ancient Egypt was an early civilization along the Nile River valley, known for its polytheistic society, writing system, and significant achievements like the pyramids of Giza.
Step-by-step explanation:
Ancient Egypt was an early civilization that emerged along the Nile River valley in the fourth millennium BCE. It was a polytheistic society with its own writing system and was united under pharaohs for most of its ancient history. The Egyptian empire developed significant achievements, such as the construction of the pyramids of Giza and the development of a bureaucratic system.