A reverse one: Scarfolk.

See the book Discovering Scarfolk by Richard Littler [1].

"Scarfolk is a town in north-west England that did not progress beyond 1979. The entire decade of the 1970s loops ad infinitum. In Scarfolk children must not be seen OR heard, and everyone has to be in bed by 8 p.m. because they are perpetually running a slight fever..."

[1] https://www.goodreads.com/book/show/20493657-discovering-sca...

Whole New Zealand doesn’t exist https://www.reddit.com/r/MapsWithoutNZ/

Yes, my girlfriend and I routinely refer to it as "Molisn't" every time it pops up in a conversation.

In Spain, we have Teruel. Even IKEA did a commercial on the topic called "Teruel does exist!"https://www.youtube.com/watch?v=SxBvvQ2GeEc

I don't see any mention of that on the Wikipedia page:

https://en.wikipedia.org/wiki/Molise

Why does it not exist to Italians?

There is a weak meme that the US state North Dakota doesn't exist, but it's not widely known and might be inspired by Bielefeld.

In Brazil, it's a very well established fact that the state of Acre doesn't exist.