Ancient Egypt was a civilization, in what is now known as the modern country of Egypt, which was concentrated along the lower reaches of the Nile river. The history of ancient Egypt occurred in a series of stable kingdoms separated by periods of relative instability known as intermediate periods. Over eight thousand years ago hunters and fishermen were among the first people to live along the Nile river. They learned to raise animals, grow crops, and they began to build towns and villages. For almost 30 centuries, from its unification (around 3100 B.C.) to its conquest by Alexander the Great in 332 B.C., ancient Egypt was the preeminent civilization in the Mediterranean world. From the great pyramids of the old kingdom to the military conquest of the new kingdom, Egypt 's majesty has long intrigued archaeologists and historians. It has even created a vibrant field of study of it 's own, Egyptology. One of the most well known things about ancient Egypt are the pyramids. Most of these pyramids were built to be tombs for Pharaohs, ancient Egyptian rulers and their families. Over 130 pyramids have been discovered to date. Some of the most famous Egyptian pyramids can be found at Giza, which is on the outskirts of Kairo. Several of these pyramids are counted among the largest structures ever built. The largest of these pyramids is said to weigh as much as sixteen empire state buildings. One famous Egyptian pyramid was built with a 34ft wall surrounding it, the wall had 15 doors