I'm really sorry I have not yet made the new maps.
This doesn't have to be a spoiler, monti, by the way.
Anyways if you look at my map
here of what I called the "Roof" (but which is actually the 6th Floor, because the game designers kept changing their mind), imagine a door on the left hand side of the Fountain Courtyard. That leads to the actual Roof. If you go north into the Attic and up the stairs you'll end up in the Observatory.