City of the Great Machine is a strategy game set in a grim universe of technocratic Victorian steampunk. The game features the conflict between the Great Machine, an artificial intelligence network, and an alliance of Heroes. The Great Machine is either controlled by a player or is automated, which completely changes the gameplay.

The Great Machine controls the City built on mobile platforms in the sky. As the Great Machine, the player (or game AI) commands a force of perfected Servants and mechanical Guards. The Great Machine's ultimate goal is to suppress social unrest and complete its grandiose Master Plan to perfect the mankind.

The other players are Heroes working together against the Great Machine to start a revolution. They encourage discontent in the City, enlist the support of famous citizens, and inflame riots. They also attempt to prevent the Great Machine from completing the Master Plan, as it leads to the enslavement of the mankind.