One thing, to me, that is interesting about the Ancient Empire (and I'm assuming you mean the Roman Empire as you indicate in your tags Western Civilization - to 1689 making Europe) is the buidling of the Forum and the institution of Roman roads.The "Via Sacra" was the first Roman street specifically built in the city to facilitate the proper flow of people and things. This was built in the same area as the Forum. Combined, they helped to make this area the center of the city's activities.
The Roman authorities were responsible for organizing city life for efficiency for its citizens. In addtition, they constructed aqueducts for the efficient transportaion of water from outlying areas into the city. The Roman Empire contributed some good ideas concerning city and town infrastructure that others followed.