Here's the context. I'm playing Spelling Bee, a game where you have to make words from seven letters and one of the letters you have to use. Anyways I get a board with a M, E, C, A in it. Now normally you can't use proper nouns but mecca it took.

I understand that there's a secondary definition of mecca meaning the most important place to something, like Madison Square Garden is the mecca of basketball. But it still feels like a reference to the city so it should be a proper noun. For instance I can't use Rome despite it being used in two idioms that aren't necessarily referring to the actual city of Rome.