Cities are the basic unit of a player's empire in Polytopia. Cities produce income and are worth 100 points per level, and units can be trained in cities. Each player starts with one city, their capital, and additional cities are acquired from capturing villages or enemy cities. A player is eliminated when they have lost all of their cities.
Cities produce one star per turn per level. The Workshop increases a city's income by one star per turn. Capitals may produce additional income (see below). Cities that are under siege by an enemy unit do not produce any income.
Capitals can be connected to other cities, primarily through roads and/or Ports, and each city connection adds one population to both the capital and the connected city. Connected cities have a road symbol next to their name.
The cost to research technology increases with the number of cities in the player's empire. For each additional city, research costs increase by one, two, or three stars for T1, T2, and T3 technologies, respectively.
The maximum number of units a city can support is equal to the number of population bars (shown below the city's name) it has, or one more than the city's level. Dots in population bars represent the units supported by the city; if every population bar has a dot in it, no more units can be trained there until space is cleared.
If a unit captures a city or village, then it will be supported by that new city instead of the city it originally was supported by. Units that are removed by death or the Disband ability also no longer take up any space.
Units will show which city they belong to in their information box. Some units may not belong to any city, such as those with the independent skill.
Cities can be leveled up by gaining population. Upgrading a city to level n from the previous level requires n population. Upgrading a city increases the income it produces by one star per turn, its unit capacity by one, and its point value by 50 points.[note 1] Upgrading a city offers a choice of one of two rewards:
- See Score for more details.
A player's capital is their starting city. In-game, capitals have a crown icon next to their name and have an underlined name.
The starting income of a capital varies by the type of player that controls it (human or bot). Capitals of easy bots produce one star per turn, those of human players and normal bots produce two, those of hard bots produce three, and those of crazy bots produce five.
The city castle is a decorative structure found in capitals. Every tribe has a unique city castle, but all are narrow square pyramids with a crown on top. If a capital is captured by another player, its city castle will remain.