City

The city first appears in the city phase but remains prevalent throughout the rest of the game. Its entire architecture is user-created, and it acts as the base from which you can buy vehicles, the UFO or more buildings.

Layout
The layout of the city is determined by the player. As mentioned before, it consists of the player's custom creations made in the building editor. In GDC '05, the city had pre-made sidewalks on ground level. As of E3, the sidewalks had been replaced by a more streamlined, apparently user-created, floor with no definite endings. This is evident in the greenness of the Greevil city floor and the mech-industrial look of the home city floor. Pedestrian versions of your creatures wander around the city. In the case of E3 when the UFO was made, some stood and watched the aircraft being created. Fireworks were launched once the construction process was completed. Buildings may also be created outside of city walls, such as turrets.

Civilization stage
In the civilization phase,you control one city. You must build up your city, and keep the inhabitants happy. At the same time, Your goal is to unify the planet by economic, military, or religious means. Cities are made individual by different architecture and building types. Once all cities on the planet are conquered or assimilated, you can buy the U.F.O from the main building and enter Space Phase

Space stage
In the galactic phase, the city plays another important role. They gather resources for your race to use and contribute in terraforming planets. There are two types of cities in this phase; colonial and home cities.

Colonies
Colonies are cities set up on worlds not belonging to you. They aid in terraforming. The better the environment the planet presents, the more resources you can draw from the planet. If the atmosphere is not yet viable, the colony forms a biodome around itself, or you can use Terraforming to make the atmosphere suitable for your race. It is not yet possible to build a colony underwater, and they must be placed near a spice geyser to collect resources. You may attack colonies with your UFO, or others may attack yours, though usually only if the race who owns the UFO is hostile, or they may be raiding your spice if they are pirates. The max limit to colonies allowed on a single planet is three, giving you a possible haul of 15 spice, 30 using an upgrade. You can only build one colony per terra score, eg. if the planet's terrascore is 1, then only one colony can be placed, there is also a limit to the amount of buildings placed depending on T-Score. There are repercussions for attacking colonies, such as a race declaring war, severing an alliance or trade route, and attacks on your colonies and home planet.

Home Cities
Home cities are all the cities on your home world which you captured during the civilization phase. They may also be attacked by other races. Your home planet gives you a total resource limit of 50 spice, but the production of each city is far less than those of your colonies. Capturing an enemy planet, be it through war or economic means, converts all the cities on that planet to your faction, converting all buildings, vehicles and spice production to yours.