CivWorld is a spin-off from Civilization featuring similar thematics but different gameplay.
The game is a massively multiplayer online game with a persistent game world. In the game each player controls a single city within a civilization. Just as in Civilization civilizations will compete with each other through war and diplomacy, but this time all players within a civilization must try to work together. Cities can assign workers to various buildings which generate resources (culture, science, food, gold and production) which can improve the civilization's overall capability in the field of battle, for researching new technologies, building wonders, etc. Building the city happens on an isometric tile based map where different building types can be constructed and upgraded to create a certain output for the city. This output is added to the city periodically (and persistently).
Resources can be traded for or with gold on the market. The amount of gold a resource is worth is determined by all recent trading done by other players. I.e. if many people start selling the same resource it will become worthless.
Combat is initiated by the ruler of a civilization but all inhabitants have their chance to supply units for the battle. Once a battle is announced it will take some hours before it launches during which times players from both attacker and belligerent sides can assemble their armies. It is also possible to send troops to help defend a foreign civilization or to attack barbarian tribes.
Aside from the main mechanic of building and optimizing the city there are also several mini-games that can be played to gain resources. Included are a Pipe Mania variant (plot caravan routes for extra gold), a tile laying puzzle (reassemble famous paintings for culture) and a maze game to discover new technologies. The latter two are played with multiple players simultaneously.
As in the original Civilization eventually one civilization will one through one of the victory goals. At that time the game will start anew. Different from most Facebook games CivWorld doesn't provide a single game world where all players are connected, instead there are many separate games with a limited number of players in progress at any time.