There isn't a specific location or date for the "discovery" of "flat stone land" because it's not a real place. It seems like you might be asking about a fictional location or a misunderstanding of a real place.

If you're thinking of a specific place, can you give me more information? For example:

* What kind of story or context are you thinking about? Is it a book, movie, game, or something else?

* Are you thinking of a specific name for this place? If so, what is it?

With more information, I might be able to help you understand what you're looking for!