Walls began to rise around cities throughout Mesopotamia shortly after urbanization began in the region c.4500 BCE. City walls were constructed to include gates and watchtowers and usually a ditch running around the outer perimeter of the wall which could be filled with water. King Hammurabi surrounded his city of Babylon with more impressive walls than usually seen shortly after he assumed the throne in 1792 BCE, but the credit for transforming the city of Babylon into an awe-inspiring wonder belongs to King Nebuchadnezzar II. Nebuchadnezzar II (634-562 BCE) built three walls around Babylon at heights of forty feet and so broad at the top that chariots could race around them. The Ishtar Gate in the wall of Nebuchadnezzar II’s Babylon was claimed by some to be greater than any of the listed Wonders of the Ancient World. The Greek historian Herodotus claimed that "Babylon surpasses in wonder any city in the known world" and specifically praised the walls which he said were 56 miles (90 kilometres) long, 80 feet (24 kilometres) thick, and 320 feet (97 kilometres) high. Although it is generally believed that Herodotus exaggerated the majesty of Babylon, other ancient writers have also noted the magnificence of the walls.