Can I change the "product tag" in "cities"

Can I change the "product tag" in "cities".
I would like to have "product categories" and "products cities".
Products categories is already there so i think I could use the tags as cities if there is not a better way.

Also: Could they be global categories and global cities for the main site as well for the other sites?

Thank you for your reply.

Regards,
Pat