I remember reading a long time ago about a city (I think in Germany) that helped protect the citizens from daytime bombing raids by having mesh stretched out above the city. This mesh was painted to look like something other than it was.
Mesh stretched over the lake (if I remember correctly) was painted to look like factories/houses, and mesh over factories and houses was painted to look like forest and lake.
Did this actually happen?
Not exactly a city, but aircraft factories on U.S. west coast were camoed like that. [Article here.] (http://www.taphilo.com/history/WWII/USAAF/Boeing/)
Mesh stretched over the lake (if I remember correctly) was painted to look like factories/houses, and mesh over factories and houses was painted to look like forest and lake.
This sounds like what Hamburg did. There is a lake (well, it's actually a dammed up river) in the middle of the city. This lake is divided into an "inner" and an "outer" part by a set of bridges for cars and trains. It's really distinctive. Since this rail bridge is incredibly important for the functioning of the northern german rail network, it was disguised by a cover over the entire "inner" part of the lake and a fake bridge out on the "outer" part.