The first thing to check are if you have scenery installed where you are expecting towns or cities. You can do this by either :
1) Running the installer and picking "Add or remove scenery" and proceeding through the screens until it shows you the map. Colored in tiles have been installed. Then you can add or remove more scenery, or just quit if you don't want to make any changes.
2) More advanced: You can also look in the folders in Global Scenery -> X-Plane 10 global scenery -> Earth nav data. The folders in here are organized by lat/long of the bottom left corner of the scenery tile. For example, the folder -20+130 contains all the scenery tiles for the middle/top of Australia shown on this map.
Another thing to check is your rendering settings. If you have them turned down too low, objects (like buildings) can disappear. Check that the number of objects & airport detail are not at minimum settings (none and low, respectively).