Hammurabi, the sixth ruler of Babylon's First Dynasty, oversaw major construction projects in Babylon, transforming it from a small town into a great city. To expand his empire, Hammurabi embarked on a series of conquests. He first raided a number of towns and cities before defeating the major powers to Babylon's north, east, and south. By the end of his reign, he had conquered all of southern Mesopotamia and a portion of Assyria. Hammurabi was a ruthless ruler. He instituted a bureaucracy based on taxation and centralised government. Under Hammurabi, the First Dynasty of Babylon reached its zenith in terms of territory and power. However, he is best known for his legal code, known as the Code of Hammurabi.