Talking about cities that dont exist... Bielefeld is the nearest bigger city (pop. about 300,000) from here. With the beginnings of the internet, someone created a conspiracy theory, saying that Bielefeld does not really exist (with fotos of motorway exit signs which had the name crossed out as proof). It was just meant to be a little joke, but soon went viral. Just about everybody in Germany knows it, and even a lot of people in neighbouring countries, who never heard of Bielefeld before, until it was said to not exist. Kind of weird...
Anyway, this is going on for 20 years now or so. To stir it all up a bit and bring Bielefeld back into the headlines, the tourist board has now put up a 1 million Euro reward for the person, that first can prove that Bielefeld does not exist.
Which holds a bit of a dilemma - if you can prove it does not exist, where would you go to pick up the money?
However, the city is back in the headlines, so thats already a success.