If you create a city or town on a computer, you can play the role of civic developer and designer. It's a lot of fun for many people. Unless you're a knowledgeable computer programmer, you'll likely need to buy or borrow a city building game or 3-D authoring tools before you can create a city or town of your own.
Step1
Download free city building game software from the Internet, if you're doing it for fun. Sites like Download.com are good sources. Step2
Consider buying the game, but if you're just trying out to see what it's like to create a city or town on a computer, then you should try it for free. Or you can purchase 3-D authoring tools from any computer store to build a non-interactive city from scratch. Step3
Determine a target platform for either interactive or non-interactive computer cities. A platform is the percentage you'd like each element to take up when you create a city or town on a computer. Elements to consider include terrain, buildings, streets, furniture and landscaping. Step4
Build low-density residential and commercial zones first for an interactive city. Once these are established, you can move up to medium-density zones. Step5
Manage funding. If you're playing a game, you will need to manage the funding for your services so that you don't run out of money while you play. You also need to manage funding if you're simply creating a digital city as realistically as you can. You need to know how much each building will cost the city. Step6
Prepare for your city for natural disasters or other potential problems. Some interactive city building games include events like fires, earthquakes, storms or riots as problems for the city planner to solve. 
