Although you can use CityGen3D just as a terrain and landscape generator, there are also various tools available to make urban environments.
The roadside object spawner is a quick way of filling out your scene because it can instantiate lots of prefabs that are automatically placed around roads.
These prefabs can be anything you like, such as houses and street lights.
You are able to limit certain prefabs to specific surface types. For instance, to ensure homes are only instantiated in residential areas and shops are generated in commercial areas.