To max out your resources means to reach the greatest production possible for a city. Maxing out resources in a capital city can be a long, painful, and expensive process that can leave you vulnerable to enemy attacks. If the player does not belong to a very large (perhaps the largest) alliance or if the player's city is not located very far from other large players the city is at risk of takeovers and farming. It is highly suggested the player use gold to speed up the process as some final upgrades without gold can take well over 300 hours to complete making it impossible (or nearly so) for this accomplishment.