Knowledge skills -- what do they reveal?

[Li Shenron]

I mean the ones nobody takes. Somebody in my PbP game took Knowedge Local, (cross-class!) and I want to make sure I reveal anything relevent when it's appropriate. Would it work locally anywhere or just his home city?

When I was the DM, our adventures took place in "The North" (Faerun). We were NOT actually playing a FR campaign, but I happened to have a map of the whole North, and that was the starting point of all our game

I used Knowledge(Local) to answer questions about the whole North, which is pretty large actually. If a PC was from a location such as a town or a forest he knew a lot if not everything about it, without needing the Kno(Local) skill at all. But usually they were from small quite places (or otherwise from outsides the continent) where no dangers would have provoked an "andventure of opportunity".