Population capacity or pop cap, is the maximum amount of units your civilization can have. In the beginning of a random map game, the population cap for all players can be set, and the number will be divided equally to each player. In campaign mode, the population cap is pre-set. One civilization bonus, 15% pop cap, can increase the amount of units a player has.

The Wonder Colosseum increases the population capacity of the player who creates it and lowers it for all enemies.