City Ruins are the remains of cities destroyed by choosing the "Raze City" option after you have successfully occupied a city. You can Raze an occupied city at any time. Not to be confused with ancient ruins. Also a result of using nuclear weaponry on cities with little defense and hit points.
City Ruins are the remnants of cities destroyed in the game. They are of no particular value in themselves, but they often sit atop valuable locations. A worker may clean up a City Ruin or simply replace it with another improvement.
Brave New WorldEdit
In Brave New World, upon the discovery of Archaeology, city ruins can be turned into an archaeological dig site that can be turned into a landmark or dug for cultural artifacts, producing either Culture or Tourism, depending on what is chosen.