I believe that books for tourists are filled with inside jokes. A booklet for tourists called Welcome to Tokyo published by the Tokyo Metropolitan Government says the following about a place called Nakamise:
Both sides of the 250 m street from [A] to [B] are lined with about 90 stores dating from the Edo Period.
The Edo Period ran from 1603 to 1868, which few readers will know. The street is actually lined with stores selling the usual tourist stuff.
I wonder whether this is a possible defense against plagiarism. Atlases, too, contain fictitious town and other features, and I believe some encyclopedias do too. The point being that if someone copies the facts — the street is 250 metres long — they could have done the research themselves independently. If they copy the fiction — lined with shops from the Edo period — they must have plagiarized.