Clairaudience-Clairvoyance - from the spell, "but the locale must be known – a place familiar to you, or an obvious one"
A familiar place just needs to be within range, but what does "or an obvious one" mean.
If the character is outside of a building the've never been in and there is NO way to see inside it (or outside a door in a dungeon... no key hole)... is it an "obvious place" to just place the Clairaudience-Clairvoyance eye within the never-before-seen building.
If you see a ship in the harbor a couple hundred feet away... is inside the hull of the ship and obvious place, even though the diviner can't see within it and has never been there?
In both cases I would say yes. If you know where the place is, you can scry on it, even if you have never been there or seen it.
An example of where you can't scry. If you have found a tunnel, and you can't see its end, you cannot scry on "the place where the tunnel leads to", since you don't know where that place is.
You cannot also scry on "the place where the BBEG is" unless you know where he is.