Just prior to the end of World War I, French officials began constructing a Potemkin Paris outside of the real city to throw off German bombing raids. This tactic may seem unusual, but aerial bombing technology was still a bit of a novelty in 1917. Planes couldn't support massive payloads, and pilots didn't have the luxury of fancy navigational technology. This faux Paris was never finished, but as you can see the fake city's layout in this article from a 1920 issue of The Illustrated London News.
[Via Ptak Science Books]