In the Commonwealth add-on there is a map 'Linking Up & Breaking Out', which has a 5 storey castle. If you place a unit in the northeast turret on the top floor, and look out northeast over nothing but farmland, low hedges, and fences, for the most part the LOS is blocked when there are no obvious obstacles. In fact, moving the LOS line a mere millimetre or two to one side or the other can result in a clear LOS being blocked. Again, there is no obvious reason why this should be given the relative empty nature of the terrain. A 5 storey building looking out over farmland should be a great location to place observers, but it is of limited value because of the way the game calculates LOS obstructions. It doesn't even come close to simulating the real world - which is a shame given how much attention is given to other aspects of simulating the subject matter.