At the height of the First World War, France made a very interesting strategic decision: they built a completely fake Paris to fool German bombers. It had a Champs-Elysee and Gard Du Nord, and many other features that are famously from Paris.
The details of this well-kept secret emerged during the 93rd anniversary of the Armistice. The Le Figaro newspaper discovered that military engineers thought that German pilots could be fooled into bombing a fake city instead of the real one.
Located on the northern outskirts of Paris, it had fake streets and electric lights – even replica buildings of Paris. The key was the perfect copy of Gard Du Nord: the famous station where trains travel at high speeds to and from London. Even local Parisians knew nothing about the dummy city, of course, this type of plan was kept a secret. It just goes to show how well prepared military planners were when they realized the threat of aerial bombardment.
The scheme was launched in 1918 as radar was really only in its infancy at the time, the long-range heavy bombers used by the German Imperial Air Force were very primitive, called the Gotha. Their crews would simply hold bombs by their fins and drop them over their targets, like Paris or London.
This fake city was built about 15 miles from the center of Paris and featured famous parts of the city like the Arc de Triomphe and the Opera. But despite the acute planning it was never really finished and never really tested, with the last German air raids ending in September 1918. After the war, it was quickly deconstructed and built over. All in all, Paris came out of World War I largely undamaged whereas London was heavily bombed & saw thousands of civilian casualties.