Officials in Bielefeld said Wednesday they'll give 1 million euros ($1.1 million) to the person who delivers solid proof of its non-existence.
They said there are "no limits to creativity" for entrants, but only incontrovertible evidence will qualify for the prize.
The idea that Bielefeld doesn't exist was first floated by computer expert Achim Held, who posted the satirical claim on the Internet in 1994 in an effort to poke fun at online conspiracy theories.
Even German Chancellor Angela Merkel once jokingly cast doubt on the existence of Bielefeld, which is allegedly located about 330 kilometers (205 miles) west of Berlin.
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