As the map may spoil a bit, here is a low spoil map made to help you to navigate easier through the Lower Underrail and the Underpassage (weaklin' not allowed!).
Green hexagone : Cities
Orange square : Quest related area or just dangerous area (avoid thoses to keep them clean for the quests)
Dotted connexion line : May be not accessible early.
And I've added a zip attachement with the .dia files if you want to annote the maps.
You can open and edit them with :
http://dia-installer.de/Other map after the new year evening