Paris

 is the capital of. It was liberated by Allied Forces in four days in Call of Duty 3. It is a major battleground in Call of Duty: Modern Warfare 3.

Call of Duty 3
Paris was captured by the Germans on June 14, 1940. In July–August 1944, a major Allied operation was untaken to break out of Normandy and capture the city. The Allies took the city on August 25. This forms the framing story for the campaign in Call of Duty 3.

Call of Duty: World at War
It is briefly seen in Call of Duty: World at War and Call of Duty: Black Ops in the Zombies map Der Riese. A picture of a zombie in front of the Eiffel Tower is seen.

Call of Duty: Black Ops
The Zombies map, Moon, was originally planned to be a map based in Paris as hinted by Moon's console codename, "zombie_paris".

Call of Duty: Modern Warfare 3
In 2016, Paris is attacked by the Ultranationalists in Call of Duty: Modern Warfare 3 for an unknown reason, setting the stage for the Battle of Paris. It is also the place where the multiplayer level "Resistance" and the singleplayer levels "Bag and Drag" and "Iron Lady" take place. Before the events of "Bag and Drag", it has been the victim of a chemical attack, the very same that killed the Davis Family.

Trivia

 * The picture on Der Riese of a zombie in front of the Eiffel Tower was foreshadowing a Zombies map in Paris but was replaced by Moon. A picture of Call of the Dead can also be seen.
 * In Modern Warfare 3, the Eiffel Tower collapsed in a similar manner to the G.I. Joe movie.